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Title: How to Install Electric Bells, Annunciators, and Alarms. - Including Batteries, Wires and Wiring, Circuits, Pushes, Bells...
Author: Schneider, Norman H.
Language: English
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  HOW TO INSTALL

  Electric Bells, Annunciators,
  and Alarms.

  INCLUDING

  _Batteries, Wires and Wiring, Circuits, Pushes, Bells,
  Burglar Alarms, High and Low Water Alarms,
  Fire Alarms, Thermostats, Annunciators,
  and the Location and Remedying
  of Troubles._


  BY
  NORMAN H. SCHNEIDER,

  Author of “The Study of Electricity for Beginners,” “Care and
  Handling of Electric Plants,” etc., etc.


  SECOND EDITION, ENLARGED

  NEW YORK
  SPON & CHAMBERLAIN, 123 LIBERTY STREET

  LONDON
  E. & F. N. SPON, Limited, 57 HAYMARKET, S.W.

  1913



  [No. 4]

  Copyright 1904
  Copyright 1913
  By SPON & CHAMBERLAIN

  The Camelot Press, 16–18 Oak St., New York



PREFACE


Among all the applications of electricity to domestic or commercial
uses, few are as widespread as the electric bell. Practically every
building used for a dwelling, storage or manufacture requires an
electric bell, annunciator or alarm system.

This book was written to explain in practical language how an electric
bell system operates and how it is installed; its success shown by its
large sale has resulted in this new edition which brings the subject up
to date.

Many new diagrams of annunciator and burglar alarm systems have been
added, together with descriptions and illustrations of wiring elevators
for electric bells, wiring for door openers, the use of transformers
for furnishing suitable ringing current from electric light circuits;
and high voltage bells intended to be used on other than the customary
low voltage battery circuits.

The author expresses his acknowledgment to the Western Electric
Company for diagrams of door opener circuits in connection with their
interphone systems, to Edwards and Company of New York for diagrams of
fire alarms, burglar alarms and annunciators, and to the Westinghouse
Company for illustrations of bell-ringing transformers.



CONTENTS


  INTRODUCTION

                                                                   PAGE
  Introduction. The principle of an electric bell.                  ix


  CHAPTER I

  The Leclanche cell--Polarization--Setting tip--The dry
      cell--The gravity cell--Connecting up cells                    1


  CHAPTER II

  The single stroke bell--The shunt bell--The differential
      bell--The continuous ring bell--The waterproof bell--Forms
      of gongs--The buzzer--Long distance bells--The relay--The
      push--Three point or double contact push--Floor push--Door
      pull--Indicating push                                          9


  CHAPTER III

  Bell wires--Joints--Running wires--How to put up a door
      bell--Combinations of bells, pushes and batteries--Faults
      in bells, faults in wiring--How to locate and remedy faults   23


  CHAPTER IV

  Fire alarms--Thermostats--Metallic thermostats--Mercury
      thermostat--How to connect thermostats--Water level
      indicators--Burglar alarms--Open and closed circuit
      alarms--Window, door and shade springs--Alarm matting--Yale
      lock alarm--Door trip alarm                                   40


  CHAPTER V

  The annunciator drop--The needle or arrow drop--The pendulum
      drop--Wiring up annunciators--Return or fire call
      systems--Double wire system--Western Electric single wire
      system                                                        55


  CHAPTER VI

  Three-wire return call system--Installing elevator
      annunciators--Burglar alarm annunciators--Clock
      alarm circuit--Bells for high voltages--Bell-ringing
      transformers--Combination bell, door opener and telephone
      circuits--Fire alarm circuit--Interior fire alarm
      system--Fire alarm system for considerable areas              64



LIST OF ILLUSTRATIONS


  FIG.                                                            PAGE
   1  Electric bell, push, and battery                               x

   2  Leclanche cell                                                 1

   3  Dry cell                                                       4

   4  Gravity cell                                                   5

   5  Vibrating bell                                                10

   6  Single stroke bell                                            10

   7  Shunt or short circuit bell                                   10

   8  Continuous ring bell                                          13

   9  Waterproof bell                                               14

  10  Dome gong                                                     15

  11  Tea gong                                                      15

  12  Cow gong                                                      15

  13  Sleigh bell gong                                              15

  14  Spiral gong                                                   15

  15  Relay and circuit                                             16

  16  Door push                                                     19

  17  Pear push                                                     19

  18  Door push                                                     19

  19  Wall push                                                     19

  20  Floor push                                                    20

  21  Door pull attachment                                          22

  22  Wire joint first operation                                    25

  23  Wire joint second operation                                   25

  24  Wire joint insulating                                         25

  25  Section of house showing wiring                               29

  26  Bell with ground return                                       30

  27  Pushes in multiple                                            31

  28  Bells in series                                               31

  29  Bells in multiple                                             31

  30  Two bells and two pushes                                      32

  31  Two bells and two pushes                                      32

  32  Two bells, two pushes and one battery                         33

  33  Double contact push                                           33

  34  Grounded bell                                                 34

  35  Tongue test of wiring                                         38

  36  Knife test of wiring                                          38

  37  Knife test of wiring                                          39

  38  Metallic thermostat                                           40

  39  Mercury thermostat                                            41

  40  Mercury thermostat circuit                                    42

  41  Water level alarm                                             44

  42  Lever water level alarm                                       45

  43  High or low water level alarm                                 45

  44  Window spring for burglar alarm                               47

  45  Burglar alarm--closed circuit                                 47

  46  Special bell connection for burglar alarm                     48

  47  Special bell connection for burglar alarm                     49

  48  Burglar alarm and relay                                       50

  49  Window-shade contact spring                                   51

  50  House wired for burglar alarm                                 52

  51  Door trip alarm                                               53

  52  Annunciator drop                                              55

  53  Needle drop                                                   56

  54  Needle drop indicating                                        56

  55  Pendulum drop                                                 57

  56  Annunciator drop circuit                                      58

  57  Simple annunciator circuit                                    59

  58  Annunciator and fire call circuit                             60

  59  Single-wire room and fire call                                61

  60  Three-wire return call circuit                                65

  61  Elevator bells and annunciator circuit                        67

  62  Burglar alarm annunciator circuit                             69

  63  Clock alarm circuit                                           71

  64  Bell-ringing transformer                                      73

  65  Bell-ringing transformer with three secondary voltages        73

  66  Western Electric interphone system                            75

  67  Western Electric interphone system for more extensive
        service                                                     77

  68  Fire alarm circuit                                            79

  69  Interior fire alarm circuit                                   81

  70  Fire alarm circuit for considerable areas                     82



INTRODUCTION


An electric bell depends for its action on the fact that a piece of
iron wound with insulated wire becomes a magnet and will attract
another piece of iron just so long as an electric current is allowed to
travel through the wire.

The instant the current ceases, the magnetism also ceases, and the
attracted piece of iron (termed the armature) is no longer held in
contact.

The general construction of an electric bell is shown in Fig. 1. _M M_
are coils of insulated wire wound on soft iron cores. _A_ is a soft
iron armature mounted on a flat spring so that it is normally kept a
slight distance away from the soft iron cores. _S_ is a brass screw
with a platinum tip touching a platinum disc on a spring attached to
the armature.

When the push button _P_ is pressed down, its two brass springs touch
each other, the current from the battery cell _B_ then flows through
the wire _W_, through the push _P_, through the coils _M M_, along _A_
to the platinum disc, out at _S_, which touches this disc, and back to
the battery.

[Illustration: FIG. 1]

The instant this is done the current causes the iron cores to become
magnets, they attract _A_, which then breaks contact at _S_. The spring
mounting of _A_ causes it to jump back to its first position, _S_ then
touches the platinum disc again, the current flows as before, and the
armature is again attracted only to break contact with _S_ and fly back.

This continual making and breaking of the circuit keeps up as long as
the push is pressed, a ball mounted on _A_ by means of a rod strikes
against the gong _G_ causing a continuous ringing of the bell. The
wires leading between the bell, battery cell and push must all be
insulated, that is, covered with cotton, rubber, etc., which prevents
the leakage of current should two wires cross each other. Copper wire
is mostly used for circuits indoors, the details of the kind and size
of wire will be given later on.

The main parts of an electric bell circuit are then--the battery to
supply the electric current; the circuit, or wires, to carry this
current; a push, or circuit breaker, to control the current flow; and a
bell to utilize the current.



CHAPTER I

_The Battery_


=The Battery Cell.= The battery cell most used in electric bell work is
the Leclanche, or some modification of it.

[Illustration: FIG. 2]

The Leclanche battery cell is shown in Fig. 2, where _J_ is a glass
jar, _Z_ a rod of zinc, and _P_ a jar of porous earthenware containing
a carbon rod surrounded by powdered carbon and peroxide of manganese.

In setting up this cell about four ounces of sal ammoniac (chloride of
ammonia) are put into the jar and enough water added to come about half
way up the jar.

The porous jar _P_ and the zinc _Z_ are then inserted, and the cell is
ready for use in a few minutes after the liquid has soaked through the
earthenware into the carbon-manganese mixture. Water is often poured
into the porous jar through holes in its top to hasten this wetting.

Wires are clamped by nuts or set-screws to the negative terminal on the
zinc or the positive terminal on the carbon, it generally not being of
consequence which terminal is attached to either wire of the circuit.

A battery cell could be constructed without the manganese, using
simply a plate of carbon and a rod of zinc, but hydrogen gas would be
generated on the carbon plate when the cell was working and would stop
the current flowing.

This is called polarization, and peroxide of manganese is a
de-polarizer, because it combines with this hydrogen gas almost as fast
as it is generated, and prevents, to a great extent, the polarization.

But it does not stop it entirely, as will be seen if the Leclanche cell
is kept working above its capacity. Then the hydrogen is generated too
fast for the manganese to destroy it, and the cell ceases to work. In
this case a rest will often restore the cell to its former power.

Cells which have been almost unable to make a bell give even a single
tap have been found good again when allowed to remain at rest over
night.

In setting up a battery cell no liquid should be splashed on the brass
terminals or corrosion will take place. Every metal surface where
connection is made to allow electric current to pass _must_ be clean
and bright, and all screws, or nuts, holding wires must be screwed up
tight so that the wires are firmly clamped.

Loose or dirty connections are the cause of probably eight out of every
ten troubles affecting bells and batteries.

When the fluid in a Leclanche cell becomes milky, more sal ammoniac
must be added. Or, better still, throw out the old solution, wash the
porous jar thoroughly in clean water, scrape the zinc bright, and half
fill the cell with fresh solution.

The zinc wearing away rapidly or becoming covered with crystals, and a
strong smell of ammonia, show generally that the cell is being worked
too hard, or that the current is leaking where it should not.

A zinc rod in a cell working the average door bell should last for six
months, the porous jar for a year.


=The Dry Cell.= The Leclanche cell being a cell with much free liquid
is liable to dry up if not watched. The dry cell (Fig. 3) is a modern
form of the Leclanche where the liquid is held by an absorbent
material, such as blotting paper, or plaster.

[Illustration: FIG. 3]

A typical dry cell[A] is shown in the figure. An outside case of zinc
is lined with blotting paper dampened with chloride of zinc and sal
ammoniac. A carbon rod is then inserted in the centre and packed around
with carbon dust and peroxide of manganese. The latter mixture is also
somewhat dampened.

    [A] For full description of this class of battery see No. 3
        Book on “Dry Batteries.”

Molten wax, or a suitable composition, is then poured on top of the
contents of the cell to seal it up and prevent the evaporation of
the fluid. A terminal on the carbon rod and another on the zinc case
complete the cell.

[Illustration: FIG. 4]

The voltage of both the Leclanche and the dry cell is about 1.45, when
it goes below this it indicates that the cell is worked out.

The two cells described are known as open-circuit cells and are only
intended for intermittent working.

When a current is needed for a long period at a time a closed circuit
cell should be used, such as the gravity Daniell cell.


=The Gravity Daniell Cell.= The gravity cell, Fig. 4, has a zinc block
_Z_ suspended from the side of the jar and a number of copper leaves
_C_ standing on edge at the bottom. A quantity of bluestone (sulphate
of copper) is poured over the copper leaves and the jar filled with
water.

During the working of this cell, copper is deposited on the copper
plate, and sulphate of zinc formed at the zinc. To hasten the action
a small quantity of zinc sulphate can be added to the solution when
setting up the cell.

The name of this cell comes from the fact that the copper solution
being heavier remains at the bottom of the jar. If the cell is not
worked enough, all the solution will become blue and the zinc will
blacken. If very dirty from this cause, remove the zinc, scrape and
wash it thoroughly. Throw out all the solution, add new sulphate and
water and replacing the zinc, then put the cell on short circuit by
connecting the copper and zinc together for a few hours.


=E. M. F.= The e. m. f. of a gravity cell is within a fraction of one
volt, its current nearly one-half ampere.

Warmth makes it give a greater current; on no account let a gravity
cell freeze.


=Resistance of a Cell.= The fluids in a cell do not conduct electricity
as well as copper does; they offer more resistance and thus reduce the
current output.

The internal resistance of a cell may be lowered by using large zinc
plates curled around the porous pot.

The Samson cell has a large zinc plate bent in the form of a cylinder,
the carbon-manganese combination standing in the centre of it.

The dry cell also has a large zinc, the internal resistance being thus
much lowered, the current output is increased. This is by reason of
Ohm’s law, which teaches that to increase the current flow, either the
voltage of the battery must be increased, or the resistance decreased.

But increased current means lessened life; there is only just so much
energy in a cell mainly dependent on the quantity of chemicals.


=Grouping of Cells.= Cells may be grouped in a battery to get increased
voltage, or increased amperage. When connected for the former, they are
in series, the carbon of one is connected to the zinc of the next, and
so on.

If all the carbons are connected together and all the zincs, they are
in multiple, and will give the same voltage as of one cell but the
combined amperage of all.

In ordinary bell work the series is the general connection, the higher
the resistance of the circuit, or the longer the wires, the more
voltage is required.



CHAPTER II

_Bells and Pushes_


=Electric Bells.= The two main types of house bells are the iron box
and the skeleton.

The iron box has a cast-iron frame, or base, and a cast- or
stamped-iron cover over the mechanism.

The skeleton bell has an iron frame but no cover, and is generally
better finished and more expensive than the iron box bells.

For fire alarm purposes, mechanical bells or gongs are made, in which
a clockwork mechanism causes the hammer to strike the gong upon being
released by electromagnetism.

Marine or waterproof bells have an iron cover fitting tight over a
rubber gasket; they are for marine, or mining, work.

Polarized, or magneto, bells are used in telephone work, and are rarely
operated by a battery, but have a miniature dynamo generator operated
by hand, or power, to supply the actuating current.

Most bells are classed for size by the diameter of the gong, a
four-inch bell being one with a gong four inches in diameter; a
six-inch bell one with a six-inch gong, and so on.

According to the use for which they are intended, bells may
be vibrating, as before described, single-stroke, shunt or
short-circuiting, differential, continuous-ringing, or adapted for
circuits of high voltage.


=The Single-stroke Bell.= The bell before described, and again shown
in Fig. 5, is a vibrating, or trembling, bell. It is often desired to
have the hammer give only one stroke for each pressure of the push, as
in signaling with a code of taps; in this case a single-stroke bell is
used. The circuit from the binding posts is then directly through the
magnet coils without any break at the contact screw, as in Fig. 6.

[Illustration: FIG. 5

FIG. 6

FIG. 7]

In adjusting such a bell to give a clear sound, press the armature up
against the iron magnet cores and then bend back the hammer until it
just clears the gong. The spring of the hammer wire will carry the
hammer sufficiently forward to hit the gong. The tone will be clearer
than if the hammer dampered the gong by pressing against it when the
armature was nearest the core.

By bringing out a third connection, a vibrating bell may be made both
single stroke and vibrating.


=The Shunt Bell.= There is a form of bell, Fig. 7, known as the shunt,
or short circuit bell, which is often used when two or more are to be
connected in series, as will be seen in the description of circuits. In
this bell the circuit through the magnets is not broken at the contact
screw, but the forward movement of the armature short circuits the
coils.

As the short, or shunt, circuit is very much lower in resistance than
the wire on the magnet coils, the main current flows around the latter
and they do not become energized. The sparking at the shunting contact
screw is much less than it would be at the ordinary breaking contact
screw, and the platinum points last longer.


=The Differential Bell.= Sparking at the breaking contacts of an
electric bell is detrimental to the platinum points, and many remedies
have been devised to overcome it.

Sparking is due to the self-induction of one turn of the wire coil
acting on its neighbor, and this property is utilized in the gas
engine, or gas-lighting spark coil, where a fat spark is needed to
ignite gas.

The differential bell has two windings in opposite directions. The
action of one would be to produce an N-pole at one end and an S-pole
at the other. But the second coil produces poles just the opposite, as
the polarity of a magnet depends on the direction in which the current
flows around it.

Where the current flows around the first winding the armature is
attracted and its spring contact meets the contact screw and allows
the current to divide, part flowing through the first coil, the other
flowing in the reverse direction in the opposite way. One coil would
tend to produce an N-pole where the other coil produced an S-pole, and
these opposite poles would so neutralize each other that there would be
no magnetism.

The armature would therefore be pulled back by its spring when both
coils were thrown into circuit. In so doing it would cut out one coil
and the same series of operations would recommence.

As a spark is normally produced where magnetism is _lost_ by a break of
circuit,[B] no spark appears, as magnetism is _produced_ by a break of
circuit in this case.

    [B] For a full explanation of self-induction see No. 1 of this
        series.


=Continuous-ring Bell.= In some classes of bell work, such as
burglar alarms, it is desired that the bell when once started shall
continue to ring until stopped by the person called. In this case a
continuous-ringing bell is needed, such as in Fig. 8.

[Illustration: FIG. 8]

When the push _P_ is pressed, the current flows in the usual way
through contact screw _L_, armature spring _A_, magnet coils _M M_,
battery _B_, back to _P_, and the bell rings. But on the first forward
movement of the armature it releases the spring contact _S_, which
flies forward and makes contact at _U_. The circuit is now from _B_,
through _M M_, to _A_, thence through _L_ and _S_, to _U_ and back to
_B_.

The bell will continue to ring until the spring contact _S_ is moved
back and caught by the projection on the armature _A_.

A continuous-ring attachment is also made and sold in most electrical
supply stores, which is complete in itself and can be applied to any
bell.

[Illustration: FIG. 9]


=Waterproof Bells.= In Fig. 9 is an example of a waterproof bell where
the mechanism is almost all entirely encased in a waterproof brass case.

The circuit is made and broken inside the case, but the magnet cores
project through it and act on a second armature placed outside. This
second armature carries the hammer which strikes the gong and is
governed in speed by the contact-breaking armature inside.


=Forms of Bell Gongs.= In order to provide a variety of sounds, bells
are provided with gongs of various shapes.

Fig. 10 shows the ordinary form of gong. Fig. 11, a tea gong; Fig. 12,
a cow gong; and Fig. 13, a sleigh bell.

[Illustration: FIG. 10

FIG. 11

FIG. 12

FIG. 13]

A coil of steel wire is also used, as in Fig. 14, which on being struck
by the hammer gives a pleasant but not loud tone.

[Illustration: FIG. 14]


=The Buzzer.= The buzzer is the mechanism of a vibrating bell less the
hammer and gong. As the armature vibrates it makes a buzzing noise
which does not carry as far as the sound from a struck gong. It is used
chiefly for a desk call and in telephone exchange work, or any place
where general attention is not desired to the signal.


=Operating Bells at a Distance.= When it is desired to ring a bell
situated at a considerable distance from the push, the resistance of
the line becomes objectionable.

[Illustration: FIG. 15]

On lines of 500 feet, No. 18 copper wire and upwards, the battery
necessary would be very large, two small batteries and a relay would
prove more satisfactory.

In Fig. 15 the circuit of a simple form of relay is given. An
adjustable contact screw _C_ is placed where an extension _S_ of the
armature _A_ can strike it. This extension is provided with a platinum
contact. The connections are as in the figure.

When the push _P_ is depressed, the current from the main battery _M_
energizes the electromagnet _E_, and the armature _A_ being attracted,
contacts _S_ and _C_ meet. These contacts close the second circuit
containing the bell _B_ and the local battery _L_.

The relay resembles a second push near the bell, but controlled by
current from a distance instead of being depressed by hand. Its
advantage consists in it needing but a very weak current to move the
armature _A_, which is held back by a light spring, or by gravity.

The relay may then be set near the bell and the wires from the push may
be of a very great length. Battery _L_, which actually rings the bell,
will thus only have to work through a few feet of wire.


=Reducing Resistance of a Bell.= Sometimes it is desired to reduce the
resistance the bell coils offer to the current, the bell then working
over a very short line with few cells of battery. Or the bell coils may
have been wound with fine wire for large battery voltage and a long
line.

The bell coils may be put in multiple, the current then dividing and
one-half going through each spool.

Untwist the joint between the spools near the yoke or iron bar to
which the spools are attached. Join one of these ends to the wire at
the armature end of the _other_ spool and the second untwisted end to
the armature end wire of its neighboring spool. Use short pieces of
insulated wire for these extra connections.

The current now instead of having to go through one spool and then the
other, can branch through both at once.

The resistance to the current of one spool is half the resistance of
two, the current through one spool will therefore be twice that through
the two spools as at first connected. And as there are two paths
for it, each one-half the first resistance, the total will be only
one-fourth the resistance of the ordinary series arrangement.

The same size battery will therefore send four times the current
through the spools in multiple than when they are in series.

It is to be noted that the wire on one spool is wound in the reverse
direction to that on the other. The reason will be apparent if the
two spools and yoke are considered as merely one spool bent in a U or
horseshoe form.

If both spools were wound in the same direction they would be in
opposite directions when the U were straightened out, and would cause
like poles at the same ends. These poles would neutralize one another,
so that there would be no magnetic attraction.

This can be readily proved by joining together the two yoke ends and
the two armature ends of the spool wires. Then pass the current through
these two joined connections.

[Illustration: FIG. 16

FIG. 17

FIG. 18

FIG. 19]


=The Push Button.= Push buttons, or pushes, are made in a variety of
forms, with metal, wood, hard rubber, or porcelain bases.

Fig. 16 has a metal base, and is suitable for a front door.

Fig. 17 is a wooden pear push, and is attached at the end of a cord
which has the two conductors braided in it, each, however, having its
own insulation.

Fig. 18 is a plate push for an outside door.

Fig. 19 is either of metal, wood, or porcelain, and is the shape most
commonly used.

A three-point push has three contact springs. One is movable by means
of the button, one is below the movable spring, and the third is above
it.

[Illustration: FIG. 20]

When the push button is not being depressed, the movable spring makes
contact with the upper spring. But when the button is depressed, these
two springs part, and the movable spring makes contact with the lower
one.

This style of push is used for special bell and annunciator work, as
will be described later.

The form of combination floor and table push in Fig. 20 is the most
solidly constructed device of its kind. The lower part is set in a
hole bored in the flooring, the metal flange keeping it in place and
preventing its slipping through.

The floor push attachment works as follows: The central metal rod is
divided into two parts _B D_, by an insulating piece of hard rubber.
When depressed against the action of the spiral spring by the foot, the
upper part _B_ connects together the contact springs _A C_, closing the
circuit of bell and battery. These contact springs are insulated from
each other by a hard rubber block _R_.

From the table push a cord containing two insulated wires leads to the
two parts of the rod at _B_ and _D_. When the push centre is pressed
down, the push springs come together and practically short circuit _B_
and _D_, which completes the circuit of bell and battery. At any time
the centre rod may be removed, leaving a surface almost flush with the
carpet, or floor, over which furniture may be moved without injury to
the mechanism of the push.

For a floor push alone a shorter form of the centre rod is also
sometimes furnished which is not divided by insulation. The spiral
spring keeps it clear of the lower contact _A_ but enables it to always
make connection with the upper contact _B_. Pressing this rod down will
also short circuit the bell and battery so that the signal is given.

A door pull attachment, like Fig. 21, is made so that the ordinary form
of lever pull bell may be changed into an electric bell. Being screwed
up near the door pull, a wire is run from the latter and fastened to
lever _L_. When the pull is drawn out the lever _L_ turns on a pivot
and a projection presses the insulated spring _S_ against the metal
base _B_. The circuit of the bell and battery being thus closed, the
bell rings.

[Illustration: FIG. 21]


=Indicating Push Button.= A push button is made which contains in the
base a small electromagnet in series with the line. An armature on a
spring is fixed near the magnet poles. When the push is depressed,
the current travels through this electromagnet, and as the circuit is
made and broken at the distant bell, it is also interrupted in the
electromagnet. The armature vibrates in unison with the bell and thus
gives an audible indication that the bell is ringing.



CHAPTER III

_Wiring, Circuits and Troubles_


=The Wire.= The size of the copper wire used in bell work is No. 16, or
No. 18, B and S gauge, and sometimes smaller, such as No. 20 to 22. But
smaller wire than No. 18 has too much resistance, and would necessitate
a larger battery power, even if its mechanical strength were not too
low. The insulating coverings are cotton saturated with paraffin wax or
compounds.

The covered wires are variously known as annunciator, office, or
weatherproof wire, these terms being mostly for distinction of the
coverings and not for the use to which the wire would be put.

Annunciator wire has two layers of cotton merely wrapped around the
copper and then saturated with paraffin.

Office wire has the two cotton layers braided, the inside one being
filled with a moisture-repelling compound.

Both office and annunciator wires have their outside coverings filled
with paraffin and highly polished.

From the ease with which annunciator wire is stripped of its cotton
covering, the braided office wire is to be preferred. These coverings
are made in a variety of colors.

Weatherproof covered wire is mostly used for electric light work, but
the sizes given above are good for bell work, although their larger
outside diameter makes them harder to conceal.

The approximate number of feet to the pound of office and annunciator
wire is given in the table.

  =======================================
     Office Wire.    | Annunciator Wire.
  ----+--------------+-----+-------------
  No. | Feet per lb. | No. | Feet per lb.
  ----+--------------+-----+-------------
   12 |      35      |  18 |     180
   14 |      55      |  20 |     225
   16 |      95      |     |
   18 |     135      |     |
  =======================================


=Joints.= Upon the care with which a joint is made much depends, a
loose or poorly made joint will offer much resistance to the current.

The correct way to start a joint in annunciator, or office, wire is
shown in Fig. 22. About three inches of each wire to be joined is bared
of its insulation and scraped bright. The ends are then bent at right
angles to each other, hooked together and one end firmly twisted around
the other, as shown in Fig. 23. Any projecting pieces are cut off, and
the joints should then be _soldered_ to prevent corrosion.

[Illustration: FIG. 22

FIG. 23

FIG. 24]

Adhesive tape (“friction tape”) is wrapped around the joint, Fig. 24,
and pressed firmly together so that there is no chance of its
unravelling. The tape wrapping should extend across the joint and on to
about a half inch of the insulation around each wire.


=Running the Wires.= To detail all the operations of installing a
complex system of bell, alarm and annunciator wires would be impossible
from the reasons that conditions vary and space is limited. General
directions will then only be given to enable the inexperienced to run
such wires as may be needed in ordinary domestic work and to guard
against the most common causes of failure.

Wires may be run in tin tubes to prevent the depredations of rats and
mice, or they may be run with simply their own covering for protection;
it is presumed the latter is undertaken.

In a case where the building is of frame and in course of erection the
task is much simplified.

Having first decided upon the plan, number of bells, pushes, etc.
and their location, proceed to run the wires first in order that the
pushes, bells, etc. may not be injured.

But where the house is already occupied, as in the majority of cases
likely to be met with by the reader, the bell and battery may be set
first.

Take the case of an ordinary door bell with the push at the front door,
the bell in the kitchen and the battery in the cellar. If possible get
the wire on two spools; it will simplify matters if both wires are of
different colors. Starting at the push, have a foot of each wire for
connection and slack, and fasten each wire lightly to the woodwork
with staples, or double-pointed tacks, never putting two wires
under one staple nor driving in a staple so it cuts the insulation.
Some cases will require a staple about every foot, on straight runs
sometimes every three feet.

In many cases the wires can be partly concealed in the angle between a
moulding and the wall, or even in a groove of the moulding itself. When
running along a skirting, the wires may often be pushed out of sight
between it and the floor. Do not attempt to draw the wires too tight
or the changes of the weather may break the wires when the woodwork
shrinks or swells.

The wires will be, one from the push to the bell, one from the push to
the battery, and one from the bell to the battery. So it is probable
that the second wire can be run right through a small hole bored in
the flooring under the push, but inside the front door. In this case
it will be perhaps easier if the spool be left in the cellar and the
end of the wire be pushed up from below and stapled to the woodwork
near the push, leaving the cellar work to the last. Only one wire will
be run then direct to the bell upstairs and it can be better concealed
than two.

If necessary it may be drawn under a carpet and not stapled, or it can
often be forced into the crack between two boards. But if not, run it
along the skirting, following the walls until it reaches below the
bell. It is often better to go entirely around a room than to cross
below a door.

If a door must be crossed the wire may either run up one side of the
frame and down the other or laid beneath the carpet on the sill. The
former is preferable, but takes more wire.

In many houses the bell wire as well as the battery wire may be run
across the cellar beams (Fig. 25), in which case bore a second hole for
it near the push; do not draw it through the same hole as the push to
battery wire. And, of course, here work upwards with the spool in the
cellar.

Having reached the bell location, run the third wire down into the
cellar to the battery. Now connect up the push, baring an inch or so
of each wire, push them through the holes provided in the push base,
screw down the push base and clamp the wires under the washers through
which the connection screws run. Do this neatly, be sure the ends of
the wires do not stick out, cut off what is left free of the bared
ends. Then connect the battery to the wire from the push and the wire
from the bell. The last thing is to scrape and fasten the bell wires to
the bell binding posts. Do this so that they cannot come loose and that
they make good contact.

[Illustration: FIG. 25]

The bell should now ring properly when the push is pressed.

To sum up, one wire leads from one spring of the push to the bell, one
wire from the other spring of the push to the battery, and another wire
from the remaining binding post on the bell to the remaining binding
post on the battery. It is immaterial whether the zinc terminal or the
carbon terminal go to the bell or push.


=Combinations of Bells and Pushes.= One of the wires in a bell circuit
may be replaced by the ground (Fig. 26). Connection may be made to a
gas or water pipe or to a metal plate buried deep in damp earth. Any
wire fastened to such a plate must be thoroughly soldered to it or a
voltaic action will be set up, which will eat it away at the point of
contact.

[Illustration: FIG. 26]

When one bell is to be rung from two or more points the pushes are to
be connected in multiple (Fig. 27) as if they were in series; all
would have to be closed to complete the circuit.

[Illustration: FIG. 27]

[Illustration: FIG. 28]

If two bells are to be operated from one push they may be in series
(Fig. 28), but in this case one of them must be arranged for single
stroke. If both were vibrating bells the armature of one would not
vibrate in unison with the other armature and the result would be
irregular contact breaking and intermittent ringing.

[Illustration: FIG. 29]

A preferable connection for two or more bells and one push is Fig. 29,
where the bells are in multiple. This requires more current than the
series method.

[Illustration: FIG. 30]

[Illustration: FIG. 31]

To ring two bells from either one of two points, the arrangement in
Fig. 30 will answer. It requires only two wires or one wire and ground
return, but two batteries. As both bells are in multiple both will
ring, the one nearest the push being depressed ringing the loudest.
This is a disadvantage. If the series arrangement in Fig. 31 be
selected, one bell must be arranged for single stroke. Both bells will
ring with equal power.

[Illustration: FIG. 32]

In Fig. 32 only the distant bell rings, the circuit having only one
battery but three wires, or two wires and ground return.

A plan where two batteries are needed but only two wires, or one wire
and ground is in Fig. 33. Double contact or three-point pushes are
necessary here, making one contact when depressed and a second one when
not being touched.

[Illustration: FIG. 33]

In this figure only the distant bell rings.


=Faults in Bells.= On examining many electric bells it will be noted
that only one binding post is insulated from the frame when the latter
is of iron (Fig. 34). As the armature spring _S_ is in electrical
connection with the frame _F_ by reason of its metal screws and
support, the circuit may run from the insulated post _U_ to the magnet
coils, thence through the insulated contact screw _C_ through the
armature spring (when it is making contact) and through the frame to
the uninsulated post _I_.

[Illustration: FIG. 34]

This saves labor, wire and complication, but if the insulation of the
post _U_, the wires _W V_, or the contact screw _C_ be injured, the
current may take a short path back to the frame.

If _C_ were thus grounded, the bell would act as a single-stroke bell.

If _U_ were grounded, the bell would not ring at all, as that would be
a short circuit on the battery between _I_ and _U_ and the latter would
also result if the bare wire were touching the frame at _V_.

If the bare wire touched the frame beyond _M M_, that is, along _W_, it
would be a single-stroke bell, as if _C_ were grounded.

As any one of these faults is likely to occur, they should be looked
for when the bell acts imperfectly, or not at all.

A very common fault in a bell is when its armature sticks to the cores
and thus does not make contact with the contact screw. This may be from
a weak spring or because of the loss of the pieces of brass inserted in
the ends of the cores to keep the armature away from actual contact. A
piece of a postage stamp stuck over the core end will often help out in
the latter case.

A high screeching noise from the armature vibrating too rapidly but
with too little play, may be from excessive battery power or the
contact screw being too far forward. The former will generally be
detected by the violent sparking as well as the rapid vibration.

In very cheap bells the platinum contacts may be replaced by German
silver or some other metal.

Platinum is necessary because the sparking would soon corrode other
metals, but it is very expensive. To test for platinum put a tiny drop
of nitric acid on the suspected metal. If bubbles or smoke appear it is
not platinum. After applying this test in any case however, carefully
wash off and remove all traces of the acid, as it will corrode the
metal into which the platinum is riveted.

Dirty contacts will decrease the current in the bell coils and it will
not work well, if at all.

Loose contact screws and wires also give trouble. The adjusting of
the contact screw is of the utmost importance, and should never be
attempted unless it is clearly necessary.


=Faults in Line.= In looking for a fault in a bell circuit make sure
the battery is working; if only one or two cells, put the ends of two
wires attached to the terminals on the tongue: a metallic taste will
indicate current.

Then see that the circuit wires are firmly clamped in the terminals and
no dirt or corrosion on the connections.

Next examine the push button and see that the wire connections at the
springs are perfect.

If there is no movement of the bell at all when the push is pressed
in, take a pocket knife or screw driver, and touch the blade across
the push springs. If there is current flowing sparks will be seen when
the blade breaks contact between the springs. If there are no sparks,
detach the wires from the bell and twist the bare ends together. Then
try again for sparks--they may now be very minute. The tongue test is
good here.

If current is detected, examine the bell for the defects first
mentioned.

But if no current is found at the push now the wires are broken
somewhere.

First short circuit the push springs by inserting a knife blade or
piece of wire so as to touch both of them. Then touch the two wires
at the bell, one to each side wire coming from the magnet coils. If
current is up to the bell and the coils are all right, a single stroke
should result.

Replace the wires in the binding posts, clean the platinum on both
contact screw and armature spring and try the adjustment. Troubles in
the bell will be mostly similar to those before mentioned.

If no current has been obtained at either bell or push, and the battery
is in good working order, the line must be tested for a cross or break.

If the wires are touching each other (Fig. 35) at some bare spot _S_
between the bell and the battery, it will be shown by the metallic
taste upon detaching one wire from the battery and laying it on the
tongue _T_, together with another wire _W_ from the disconnected
terminal of the battery. The current will travel from the battery to
the cross at _S_, then back along the second circuit wire to the tongue
and through the short wire to the battery.

[Illustration: FIG. 35]

If no current is obtained in this way it is probable that the wire is
broken.

[Illustration: FIG. 36]

The easiest way to find this is to take a bell to the battery and
connect it between the circuit wires and the battery (Fig. 36).

Then with a sharp knife carefully cut away a little piece of the
insulation from each wire beyond the bell and battery and short circuit
the bared spots with the knife blade _K_. Keep working towards the
push. The bell will ring each time at _K K_ until the break _D_ is
passed, at _C_ it will not. It becomes an easy matter then to locate it.

[Illustration: FIG. 37]

If the bell and push are far apart, as in Fig. 37, a break between the
push and the bell may be found as shown. With the knife blade _K_ at
different points the bell will ring, but after passing the break _D_ it
will not ring.

Such simple tests as are here given can be carried out by any one, but
far better results will be obtained if the reason for each is first
learned.

This can be readily done by a careful study of the diagrams and text.



CHAPTER IV

_Alarms_


=Fire Alarms.= Thermostats, heat alarms and fire alarms are all
practically the same, the term thermostat being applied principally to
the apparatus which closes the electrical circuit.

[Illustration: FIG. 38]

Thermostats act on the principle that heat causes expansion whether of
substances, liquids, or gases.

The degree in which different substances expand varies for the same
increase in temperature. This fact is used in a common form of
thermostat shown in Fig. 38. A strip of wood or hard rubber _R_ has a
strip of thin sheet metal _S_ riveted to it. This compound strip is
held at one end by a lug _L_ screwed fast to a baseboard. Upon an
increase of temperature the hard rubber expands more than the metal
strip and the compound strip bends towards the adjustable contact
screw _A_. Upon touching the latter, the circuit through the bell _B_,
battery _C_ and the metal strip _S_ is completed, and the bell rings.
A contact screw can be arranged at the other side of _S R_, which will
give warning of a decrease in temperature, as the rubber contracts more
than the metal strip.

[Illustration: FIG. 39]

In some thermostats of this character two metals having different
coefficients of expansion, such as steel and brass, are used instead of
metal and hard rubber.

Thermostats of this nature are much used in incubators, and they can
readily be combined with electric apparatus to open or close hot-air
valves, dampers, etc., and thus regulate the supply of hot air, hot
water, or gas.

A thermostat much used in fire alarm work has a thin metal chamber
which is air tight. An increase of temperature causes the air to
expand, which swells out the walls of the chamber and closes an
electric circuit.

[Illustration: FIG. 40]

The mercurial thermostat shown in Fig. 39 has a glass tube _T_ and bulb
containing mercury. Into each end is sealed a platinum wire _P P_. Upon
the temperature rising to a predetermined degree, the expanded mercury
completes the circuit between _P P_ and the battery _C_ and bell _B_
are put in operation.

Fig. 40 is the open circuit system most used by the fire alarm
companies, only one circuit of six thermostats being illustrated.

It will be seen that if any thermostat closes the circuit between the
outer and inner wires of the ring _A B_, current will flow through the
corresponding drop of the annunciator and will attract the armature
_A_ of the relay. This will cause the bell to ring. As the relay is
connected to the annunciator as before shown for the annunciator bell,
it offers a common path for any drop to the battery. Thus the bell
will ring for any circuit, but the individual drop only will fall. In
a simpler circuit the relay may be dispensed with and a vibrating bell
only used.

Thermostats may be operated on open or closed circuits, that is, they
may give the alarm by closing a circuit and ringing a bell, or by
opening one and releasing a contact spring as in the burglar alarm
system to be described later.


=Water Level Alarms.= Where it is desired to signal the rising or
falling of water in a tank above or below a given point, a water level
indicator as in Fig. 41 may be used.

A hollow ball _H_ is mounted on the end of a rod which slides
vertically in guides, not shown. Adjustable stops _S S_ press against
a spring arm _R_, pressing it up or down, according as the water
level is rising or falling. If rising, _R_ makes contact with the
adjustable screw _A_, if falling, with _D_, in both cases completing
the electrical circuit of the battery _C_ and bell _B_.

[Illustration: FIG. 41]

Another and simpler form is shown in Fig. 42, where the ball _H_ is
mounted on the end of a lever _L_ pivoted at _P_, its rise or fall
completing the circuit of _B_ and _C_ as before.

Where it is desired to give a different signal for the rise and the
fall of level, two bells _B_ and _E_ (Fig. 43) may be used connected as
shown. The rising of the ball will ring bell _B_, and its fall, bell
_E_.

[Illustration: FIG. 42

FIG. 43]

In both forms of indicator, a means must be provided that an undue
rise may not bend the lever. This may be accomplished by using contact
springs instead of contact screws; it is, however, then harder to
adjust the indicator to fine differences of level.

In all cases the contacts must be faced with platinum to prevent
corrosion.


=Burglar Alarms.= A burglar alarm is a device for indicating the
opening of a door or window, by the ringing of a bell or operation of
an annunciator. The contact apparatus at the points to be protected
may either open an electrical circuit or close one, in the latter case
being mere modifications of push buttons. The simplest form is the
latter or open-circuit method.

The spring contact to be inserted in the door jamb or window frame is
so constructed that while under pressure the contacts are kept apart
and the circuit is open. But when the door or window is opened, the
pressure is released and a spring forces the contacts together.

Fig. 44 is an open-circuit window spring fitted in the window frame so
that when the window is closed the spring lug _S_ is pressed inwards,
breaking contact with the base _B_.

If the window is raised, the lug flies to the position shown by the
dotted lines, and making contact with _B_, completes the circuit
through bell and battery. These springs are fitted in the side of the
window frame in a vertical position and are entirely concealed when the
window is shut.

[Illustration: FIG. 44]

In the closed-circuit system the reverse happens. The pressure of the
closed door or window keeps the contacts together and its opening
enables them to spring apart.

[Illustration: FIG. 45]

In Fig. 45 is a diagram of a closed-circuit burglar alarm, _C_ a cell
of gravity battery, _R_ a relay, _F_ the fixed contact and _M_ the
movable contact of the spring, _S_ a stud projecting through the base
of the spring and pushed in by the closed door.

When the door is closed, _S_ being pushed in, the circuit of _C_, _R_,
_F_ and _M_ is closed. The magnets of the relay hold the armature arm
_A_ forward against a hard rubber contact. But when _S_ is released,
the relay circuit is opened, _R_ loses its power and _A_ flies back,
making contact, and throwing in circuit bell _B_ and battery _L_.

[Illustration: FIG. 46]

A form of bell and relay combined is shown in Fig. 46. Here the
armature _A_ is held against the magnets while the circuit through the
spring _F_ and battery _G_ is closed. But on opening this circuit the
armature flies back and makes contact with an adjustable contact screw
_S_ putting in circuit a local battery _C_. The bell is now practically
a vibrating bell; on a closed circuit it rings until the circuit is
again closed or the battery runs down.

[Illustration: FIG. 47]

A different connection of the same scheme is Fig. 47, where only
one battery is used. This must be a gravity battery or some other
closed-circuit battery. The circuit can be easily traced in the figure
and needs no special description.

Both of the latter schemes are inferior to one using a separate relay.
If the circuit at the spring were quickly closed again the bell would
either stop ringing, or be so hampered as to ring very weakly.

[Illustration: FIG. 48]

A relay made as in Fig. 48 has no spring support to the armature _A_,
which falls down by gravity. The adjustable contact _C_ is screwed
far back, so that the armature must fall a considerable distance away
from the electromagnets before it makes contact. This ensures that the
armature will not be attracted and the bell stopped from ringing by a
re-closing of the circuit at the door or window spring.

A shade spring (Fig. 49), is made for either open or closed circuits.
In operation, the shade is pulled down and its string or ring hooked
on to _H_. This draws _H_ up a trifle against a spiral spring and
its lower end makes contact with an insulated spring _S_ closing the
circuit. If the shade is disturbed, the spiral spring on the lower part
of _H_ is released and it causes a break of contact with _S_ in the
direction of the arrow.

[Illustration: FIG. 49]

When made for open circuit, _S_ is bent so that while under tension no
contact is made, but release of tension causes the contact.

Fig. 50 gives the wiring of two windows and a door on the
closed-circuit system. It will be seen that the contact springs are all
in series, opening a window or the door will thus break the circuit.

When setting the alarm at night by connecting up the batteries, relay
and bell, should any one of these springs be open the relay armature
will not hold, and the bell rings.

[Illustration: FIG. 50]

In this figure the relay is replaced by an electromagnet holding up a
drop shutter by magnetic attraction. Upon the circuit opening, this
shutter falls, exposing a number painted on it. At the same time it
hits a spring contact placed below it and closes the bell and local
battery circuit.


=Door Trip Alarm.= A swinging contact door trip can be attached over a
door to ring a bell when the door is opened.

[Illustration: FIG. 51]

In Fig. 51 the door trip is screwed over the door so that the lowest
arm _A_ is struck by the door. When the door is opened, in the
direction of the arrow, the arm _A_ is thrust forwards, and in its turn
moves the contact arm _C_, completing the bell and battery circuit. But
when the door is being closed, _A_ swinging in the reverse direction
does not move _C_ and no alarm is given.


=Miscellaneous Alarms.= The Applegate electrical matting is composed
of wooden slats with springs so arranged that the weight of any person
stepping on it will close a circuit and ring a bell.

It is intended to be put under the ordinary door mat or under stair and
room carpeting.

The Yale lock switch is a Yale lock and switch combined. Upon any key
but the right one being inserted, a circuit is closed and an alarm bell
is rung.



CHAPTER V

_Annunciators_


=The Annunciator.= The mechanism of an annunciator consists of
electromagnets which allow shutters to drop or needles to move on
the circuits being closed. A bell is also rung in most cases to call
attention to the annunciator. The number of the circuit is marked
on the shutter, or near the needle, either shutter or needle being
replaced by a reset device, which may be mechanical or electrical.

[Illustration: FIG. 52]

Annunciator drops are made in a variety of forms. Fig. 52 illustrates
the principle underlying nearly all of them.

When current flows through the magnet coils _M_, the armature _A_ is
attracted, and being pivoted at _P_, the lever hook _H_ rises and
allows the weighted shutter _S_ to fall and display a number painted
on its inside surface.

[Illustration: FIG. 53

FIG. 54]

The needle drop in Fig. 53 is one that has met with great favor and
works as follows: the soft iron core of the magnet _C_ has a hole
drilled through it, in which turns the shaft _S_. An arrow or needle
is attached at the front end over the face of the annunciator. A
notched arm _B_ is fixed on the rear end of the shaft and is held in a
horizontal position by the end of armature _A_.

When the current flows around _C_, armature _A_ turns on its pivot
towards the core of _C_, as in Fig. 54, unlocking _B_, which falls and
thereby partly rotates shaft _S_ and the arrow.

When it is desired to reset the arrow and arm, a button is pressed
upwards, which raises a rod carrying an arm _R_. This latter arm in
turn raises _B_ to its former position, the heavy end of _A_ falls, and
its pointed end locks _B_.

[Illustration: FIG. 55]

Pendulum, or swinging, signals are used in annunciator work, where
there is a liability that the ordinary drop shutter would not be reset.
They, however, only give a visible signal for a few seconds, and are
therefore liable to be overlooked.

In Fig. 55 a pivoted arm carrying a soft iron armature _A_ and a
thin plate _B_ having a number on it is free to swing in front of an
electromagnet _M_.

When the current flows in the electromagnet the armature is attracted,
and upon the circuit being broken at the push, the armature is released
and the arm swings to and fro.

The drops of an annunciator are wired up as in Fig. 56.

[Illustration: FIG. 56]

One end of each coil is attached to a common return wire _C_, the
other end going to the push _P_. When _P_ is depressed, the circuit of
any drop is through _M_ along _C_ through bell, battery and up common
battery wire _W_ back to other contact of push _P_. Depressing any push
does not therefore affect any other drop but the one controlled by it.


=Wiring up an Annunciator.= A diagram of the connections for an
annunciator with a separate bell is given in Fig. 57. Where the bell is
contained in the case a terminal will be generally found for connection.

[Illustration: FIG. 57]

The figure shows a wire running from the battery to one side of each
push button. This is the common return, or battery wire, and saves
installing two wires from each push. It should be larger, however, than
the rest of the wires, generally about No. 16 B. & S.

All the wires for an annunciator should be run before connecting
up. There are different methods of sorting out the wires at the
annunciator. One way is to connect the wires (except of course common
or battery return wires) to the drops in any order. Then an assistant
travels from push to push and presses each button, noting the room
numbers and the order in which they were visited.

As each drop falls, its number and order is noted.

Comparing this with the list made by the assistant will show the
correct changes to make.

[Illustration: FIG. 58]

For instance, suppose pushes 1, 2, 3, 4, 5 and 6 were pressed in that
order, and drops 3, 4, 5, 1, 2 and 6 fell in that order. Then the wires
at the annunciator would be changed as follows: From 3 to 1, 4 to 2, 5
to 3, 1 to 4, and 2 to 5; 6 would already be in its right place.

Another way is to commence by twisting together say the wires at No. 1
push. Then go to the annunciator and touch each of the push wires to
No. 1 drop until it falls. Then connect it, untwist the wires at No. 1,
push and connect it up. Proceed to No. 2 and so on until all the pushes
have been connected in turn.

In some cases it is desired to answer back to the person calling, or to
be able to call any person from the annunciator.

A circuit like Fig. 58 answers the purpose of both annunciator call and
return, or fire, call. This requires two wires from each room to the
annunciator and a common return wire. By tracing out the circuit it
will be seen that when a room push is pressed, the annunciator needle
and bell indicate. And when one of the pushes near the annunciator is
pressed, the corresponding room bell rings. The former circuit is from
the push, along the common return wire, through bell and annunciator
back to the push.

The fire call is from push up line to bell through bell along common
return and through battery to the push.

The Western Electric single-wire system (Fig. 59) uses three-point
pushes, two batteries and two return wires. Battery _A_ is for the
annunciator circuit and battery _F_ for the fire, or return, call.

[Illustration: FIG. 59]

In each room the top contact and push spring contact are normally
together.

If one of the pushes below the annunciator is pressed, battery _F_ is
thrown in series with the bell in the room.

But when the room push is pressed its bell is cut out and the circuit
becomes like an ordinary annunciator circuit.



CHAPTER VI

_Annunciators and Alarms_


=Three Wire Return Call System.= A three wire return call annunciator
system is shown in Fig. 60.

There are two battery wires installed, from which taps are taken off
and led to each room or push button.

Three way or return call push buttons are used as shown at points
marked _B_.

In the diagram, the bells are marked _A_, the drops in the annunciator
_D_, the annunciator bell _C_ and the return call buttons in the
annunciator _E_. The batteries are as shown at _F_. The heavy black
outline encloses the annunciator mechanism and connections which are
drawn diagrammatically for the sake of clearness.

Three stations only are shown on the sketch, but the annunciators which
are manufactured by Edwards and Co., Inc., of New York, are made in all
standard sizes.


=Installing Elevator Annunciators.= The installing of electric bells
and annunciators in elevators does not present any special problems,
although the apparatus used must be selected with a view to its being
suitable to withstand the shocks incident to elevator service.

[Illustration: FIG. 60]

In general the wires leading from the push buttons on the different
floors to the bell or annunciator in the elevator, are flexible
and made up into a cable. One end of this cable is attached to the
underside of the elevator car, the other end being fixed usually to
the elevator wall, at a point midway between the top and bottom of the
shaft.

In Fig. 61 is shown a diagram of the general circuit used, details of
course differing in each installation.

One point to be taken care of in elevator work is the attachment of
the cables. The continual movement tends to break the wires at the two
ends if good flexible cable is not used and the installation done in a
workmanlike manner.

Elevator cable is a standard article and may be procured through any
electrical supply store. That most commonly used consists of the
requisite number of copper conductors each composed of 16 strands
No. 30 B. and S. gauge soft and untinned copper wire. These flexible
conductors are insulated with two reverse wrappings of cotton and one
braid of cotton. The insulated conductors are cabled together with a
steel supporting strand where extra tensile strength is required, as
in the case of extra long cables. The number of conductors generally
ranges from 3 to 20 inclusive.

The wires leading from the push buttons to the cable should be
preferably rubber covered and braided. Only where economy at the outset
is desired may ordinary annunciator or office wires be employed.

[Illustration: FIG. 61]

A connection block carrying binding posts is used at each point where
the cable connects to the push button wires or to the annunciator. This
may be home-made or purchased ready made, as desired.


=Burglar Alarm Annunciators.= Although almost any annunciator may be
used for open circuit burglar alarm work, they usually do not contain
certain devices which are desirable in burglar alarm work.

In Fig. 62 is shown a diagram of a burglar alarm annunciator, the view
being schematic of the back board.

The references are as follows: _A_ is the main alarm bell situated
wherever desired and connected to the binding posts _BB_. The battery
connection leading directly to the battery _K_ is marked _C_ and that
leading to the contact spring is marked _D_. The cut-off switch _E_
cuts off the battery while _F_ is the constant ring switch. _G_ is the
upper bar and _H_ the lower bar, while the letters _JJ_ denote the
indicating drops. The door and window springs are lettered _S_. At _L_
is a switch which may be used to disconnect the entire burglar alarm
system. Where it is desired to disconnect only a section at a time, the
switch corresponding to the section is turned off the upper bar _G_ and
on to the lower bar _H_.

[Illustration: FIG. 62]


=Clock Alarm Circuit.= A diagram of the wiring and connections on the
back board of all clock alarms is illustrated in Fig. 63. This diagram
embodies the principles of the last described circuit, but includes the
circuit of a clock-operated alarm.


=Bells for High Voltages.= The use of electric bells on lighting
circuits is becoming quite general, as it obviates the necessity
of using batteries, and thereby simplifies both installation and
maintenance.

There is no fundamental objection to operating make and break bells
on electric light circuits. Providing the voltage and amperage are
the same, there is little difference between the current from a
direct-current dynamo and that from a battery. But owing to the higher
voltages of the lighting circuit over that generally employed from
batteries, the bell coils must be wound to high resistances to keep
down the current strength. There are also other slight changes to
assist in suppressing sparking, as have been already treated on.

Where the circuit is not over 220 volts, the bells are wound with fine
wire and have also self-contained resistance coils. For 500 volts and
over, a resistance lamp is connected in with the bell which in this
case is wound for a 150-volt circuit.

These bells up to 6-inch and inclusive will operate on circuits of
either direct or alternating current.

Above this size it is necessary to use specially constructed bells on
alternating current circuits.

[Illustration: FIG. 63]

Most large hotels and office buildings having direct current lighting
service are using it for ringing bells and similar work to the total
exclusion of batteries.

Where the number of units to be operated justifies it, motor generators
are operated in connection with the lighting mains to produce a low
voltage most suitable for the bells. The connections in this case are
no different to those when batteries are employed.


=Bell-ringing Transformers.= The best system for operating bells and
annunciators from alternating current circuits is undoubtedly that
employing small specially constructed transformers to reduce the
voltage. These transformers are being used universally for hotel and
office work where alternating current is available. They are simple,
being merely one or more coils of well insulated wire wound on soft
iron cores and having connections for both the lighting circuit and the
bell circuit.

As a general rule the coils are divided as to their number of turns or
according to the ratio of transformation desired. For example, if the
circuit were 110 volts and 10 volts was required for the bell circuit,
the total number of turns in the transformer would be connected, 10/11
to the lighting circuit and 1/11 to the bell circuit.

The bell-ringing transformers on the market are made in several
styles. One small style, Fig. 64, for single residences, is for use
on 110 volts and produces a bell voltage or secondary voltage as it
is termed, of 6 volts. Another size, Fig. 65, of this transformer has
three secondary voltages 6, 12 and 18, each of which can be used by
connecting to the right binding posts.

[Illustration: FIG. 64

FIG. 65

BELL-RINGING TRANSFORMERS.]

It is to be noted that where the lighting service voltage or primary
voltage varies from the above, the secondary voltage delivered to the
bell circuit will vary in like proportion. It should also be noted
that a careless reversing of the connections, that is connecting the
secondary leads to the lighting circuits, instead of the primary
leads would cause a like high voltage at the other terminals of the
transformer, raising it in due proportion instead of lowering it. Thus
such carelessness would produce a voltage of 2,400 volts instead of 6
if a transformer intended to deliver 6 volts from a 120-volt circuit
was wrongly connected.

The results might very well then be dangerous. All transformers are
properly marked, however, and such an error only occurs through
ignorance or carelessness.

The installation of these bell-ringing transformers is simplicity
itself; they require no care after installation and have met with the
approval of the National Board of Fire Underwriters.


=Combination Circuits.= Circuits intended primarily for electric
bells or annunciators in houses and apartments may often be also made
to serve for other electrical devices such as door openers, house
telephones, etc. This subsidiary apparatus may be installed with a
little additional wiring or perhaps will not need any other wires, as
when both the devices are not used at once.

[Illustration: FIG. 66]

Electrical door openers are great conveniences and are practically
indispensable where the outside door is on another level to the
location of the dweller or where two or more families occupy the same
house. The device is simple, consisting of an electrically released
spring-plate against which the lock bolt is normally held and a door
opening spring.

When the door opener button is pressed, the spring plate is released,
releasing the lock bolt by the same action. The door spring then forces
the door open enough to clear the opener plate, which flies back into
position when the button is released.

These door openers are made in several forms for door frames, such as
those on thin doors, iron gates, for surface or rim locks, for thick
doors, sliding doors and any other regular type of door.

The push button is the same as used for electric bells and may be
located wherever desired. The pushes are wired in multiple as shown
in Figs. 66 and 67, which are two circuits of a type of the Western
Electric interphone, a system of house telephones supplied for houses
and buildings of every size. Fig. 66 shows a circuit which provides
telephone service between the vestibule and the apartments, the door
opener wiring being clearly indicated. In Fig. 67 the circuit provides
a more extensive service, enabling the janitor, the apartments and the
tradesmen to intercommunicate in the most desirable system. The door
opener wiring is also clearly shown.

[Illustration: FIG. 67]

The convenience of having telephone connection in the house or hotel
and its advantages over speaking tubes are too well known to need
extended comment. Where electric bells have already been installed it
is quite feasible now to use the same wires for telephones also.

Telephone sets especially designed for this service are manufactured
by the Western Electric Company in their interphone series. They are
simple and compact, and may be installed by anyone who can put up an
electric bell.


=Fire Alarm Circuits.= A fire alarm circuit suitable for factories,
private plants or groups of buildings is shown in Fig. 68. It is a
series system, with closed circuit, the gongs sounding whenever the
circuit is opened whether by the contact breaker in the boxes or by the
accidental breaking of a wire. This insures that it remains in good
working order, as when any part of the circuit is opened, a warning tap
is sounded on every bell or gong.

The boxes have contact breakers which send a separate number of
impulses for each box, thus announcing the box number on each gong. The
boxes and gongs may be located anywhere, as the system is perfectly
flexible.

The reference letters in the diagram are as follows: _C_ indicates the
gongs which are preferably of the electro-mechanical type, a coiled
spring providing force for the blow, electricity being merely used to
release and retain the hammer or striker. The alarm boxes are marked
_BB_ and the battery which is of the closed circuit type is marked _D_.

[Illustration: FIG. 68]


=Interior Fire Alarm System.= Another system suitable more particularly
for indoor operation is illustrated in Fig. 69. Here the alarm is given
by breaking the glass front of an alarm box and releasing or pressing
an electrical contact.

The box sounded indicates by causing a drop to fall on an annunciator
and at the same time rings an alarm bell. The latter are generally
provided with constant ring attachments, which keep the bell sounding
until shut off.

The annunciator shown in the diagram has switches for controlling each
individual bell circuit, and also for control of the entire system.

There is no practical limit to the number of stations in this system,
it being determined by the size of the annunciator used or by other
obvious factors.

The reference letters on the diagram are as follows: _A_, alarm bells
which may be located wherever desired. _B_, break-glass alarm boxes
also located at convenient points. _C_, annunciator drops, _D_,
switches on annunciator which control each individual bell circuit,
enabling any circuit to be cut out, cut in or tested without disturbing
any other circuit. _E_ is a general alarm switch, causing all bells to
ring at once when it is operated.

The battery _F_ varies with the number of bells and boxes and the
length of line, from three cells upwards. A cut-out switch _H_ is
added to cut out the entire system by opening the battery wire. The
annunciator bell is at _I_, an auxiliary bell being added in multiple
with it when necessary.

[Illustration: FIG. 69]

[Illustration: FIG. 70]


=Fire Alarm System for Considerable Areas.= Where the area is more
extensive and the number of stations considerable, the system
illustrated in Fig. 70 is very suitable. It consists of the requisite
number of break-glass boxes, bells and a more elaborate annunciator
system. In general details it resembles the last system, but uses a
relay to send out the current for ringing the alarm bells.

When a box operates, the current impulses sent on the line act on the
relay instead of directly on the bells. Each stroke of the relay closes
a local circuit which includes the bells and the battery.

This system does away with large batteries and is very economical of
wire. The current needed for the relay is very small, whereas in a
direct system of any size, the current and voltage to ring a number of
bells located at wide intervals would be prohibitive.

The reference letters are as follows: _AA_ are the alarm bells, _BB_
the break-glass alarm boxes, _C_ is the annunciator bell, _D_ is the
relay which remains closed when an alarm comes in keeping the bells
constantly ringing until shut off. _E_ is a resistance coil and _F_ is
the battery.

A system cut-out switch _G_ and _JJ_ switches on the annunciator
for controlling individual circuits are also provided. _HH_ are the
annunciator drops and _K_ is a constant-ring switch which can also be
used for a general alarm to ring all the bells at once.



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Dubelle’s Famous Formulas.

KNOWN AS

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A NEW AMERICAN BOOK ON INDUSTRIAL ALCOHOL.


A PRACTICAL HANDBOOK ON THE

Distillation of Alcohol

FROM FARM PRODUCTS AND

DE-NATURING ALCOHOL.

By F. B. WRIGHT.


Including the Free Alcohol Law and its Amendment, the Government
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In the preparation of this, the second edition, the author has followed
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[Illustration]

Send for this to-day

Fourth Edition, Enlarged

REVISED AND REWRITTEN

ELECTRICAL TESTING

BY NORMAN H. SCHNEIDER


Contents of Chapters.

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314 pages, 150 illustrations, cloth $1.15 postpaid.

  Spon & Chamberlain,      123-5 LIBERTY STREET,      NEW YORK



Transcriber’s Notes


Punctuation and spelling were made consistent when a predominant
preference was found in this book; otherwise they were not changed.

Simple typographical errors were corrected.

Occurrences of inconsistent hyphenation have not been changed.





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