Chapter XXI: The Simple Magneto Switchboard (3)

4. What troubles were encountered in the earlier forms of granular carbon transmitters and how were they overcome?

5. What limits the current-carrying capacity of the transmitter? How may this capacity be increased?

6. State in what kind of transmitters a maximum degree of sensitiveness is desirable.

7. Show the conventional symbols for transmitters.

8. Describe a telephone receiver.

9. Sketch a Western Electric receiver and point out its deficiencies.

10. Make a diagram of the Kellogg receiver.

11. Describe the direct-current receiver of the Automatic Electric Company.

12. Describe and sketch the Dean receiver.

13. Show the conventional symbols of a receiver.

14. Describe exactly how, in a cell composed of a tin and a silver plate with dilute sulphuric acid as electrolyte, the current inside and outside of the cell will flow.

15. Describe the phenomenon of polarization.

16. What is _local action_ of a cell? How may it be prevented?

17. Into how many classes may cells be divided? Which class is most used in telephony?

18. Describe the LeClanché cell.

19. Sketch and describe an excellent form of dry cell.

20. Show the conventional symbols for batteries.

21. Sketch and describe the generator shunt switch and the generator cut-in switch.

22. How may a pulsating current be derived from a magneto generator?

23. Show conventional symbols for magneto generators.

24. Sketch and describe the Western Electric polarized bell.

25. Give conventional ringer symbols.

26. What is the purpose of the hook switch?

27. Make sketch and give description of Kellogg's long lever hook switch.

28. Describe and sketch the Western Electric short lever hook switch.

29. Point out the principal difference between the desk stand hook switches of the Western Electric Company and of the Kellogg Switchboard and Supply Company.

30. Give conventional symbols of hook switches.

REVIEW QUESTIONS

ON THE SUBJECT OF TELEPHONY

PAGES 143--225

* * * * *

1. Describe an electromagnet and its function in telephony.

2. Sketch an iron-clad electromagnet.

3. What is a differential electromagnet? Sketch and describe one type.

4. State the desirable characteristics of good enamel insulation for magnet wire.

5. If you have a coil of No. 23 double cotton B. and S. wire of 115 ohms resistance and you have to rewind it for 1,070 ohms resistance with double cotton wire, what number of wire would you take? Show calculation.

NOTE. No. 23 d. c wire has res. 1.772 ohms per cubic inch; for
the core, 115 ohms. There are required in the coil 1,070 ohms,
that is, 9.3 times as much. 1.772 x 9.3 = 16.47 ohms, which must
be the resistance per cu. in. This resistance gives, according to
Table IV, No. 29 wire.

6. What is an impedance coil? State how it differs from an electromagnet coil.

7. Describe the different kinds of impedance coils.

8. Give symbol of impedance coil.

9. What are the principal parts of an induction coil?

10. What is the function of an induction coil in telephony?

11. What is a repeating coil and how does it differ from an induction coil?

12. Give conventional symbols of induction coils and repeating coils.

13. Enumerate the different types of non-inductive resistance devices and give a short description of each.

14. Define condenser.

15. What is the meaning of the word _dielectrics_?

16. State what you understand by the specific inductive capacity of a dielectric.

17. Upon what factors does the capacity of a condenser depend?

18. What is the usual capacity of condensers in telephone practice?

19. Give conventional condenser symbols.

20. By what two methods may the current be supplied to a telephone transmitter?

21. Make sketch of local-battery stations with metallic circuit.

22. Sketch common-battery circuit in series with two lines.

23. State the objections against the preceding arrangement.

24. Make sketch of the standard arrangement of the Western Electric Company in bridging the common battery with repeating coils.

25. Sketch the arrangement of bridging the battery with impedance coils and state the purpose of the coils.

26. Make diagram of a common-source current supply for many lines with repeating coils and point out the travel of the voice currents.

27. Name the different parts which comprise a telephone set.

28. What is a magneto telephone?

29. Make diagram of the circuit of a series magneto set with receiver on the hook and explain how the different currents are flowing.

30. Show diagram of the Stromberg-Carlson magneto desk telephone circuit and describe its working.

31. Give sketch of the Stromberg-Carlson common-battery wall set circuit.

32. Describe briefly the microtelephone set.

33. Make sketch of the Monarch common-battery wall set.

REVIEW QUESTIONS

ON THE SUBJECT OF TELEPHONY

PAGES 227--286

* * * * *

1. What is a party line?

2. What is usually understood by private lines?

3. What problem is there to overcome in connection with party lines?

4. State the two general classes of party-line systems.

5. Point out the defects of the series system.

6. Make sketch of a metallic bridging line and show the circuit for the voice currents.

7. What is a signal code?

8. Give classification of selective party-line systems with short definitions.

9. Describe the principle of selection by polarity and make sketch illustrating this principle.

10. Make diagram of the circuit of a four-party station with relay.

11. Describe the process of tuning in the harmonic system.

12. What is the difference between the under-tune and in-tune systems?

13. Sketch circuit of Kellogg's harmonic system.

14. Illustrate the principle of a broken-line system by a sketch.

15. In what particulars does the party-line system in rural districts differ from that within urban limits?

16. Describe and sketch Pool's lock-out system.

17. Make diagram of the K.B. lock-out system.

18. What is the object of the ratchet in this system?

19. Make diagram of simplified circuits of Roberts system.

20. Sketch and describe Roberts latching key and connections.

21. Sketch circuits of bridging station for non-selective party line.

22. How would you arrange the signal code for six stations on a non-selective party line?

23. What is the limit of number of stations on a non-selective party line under ordinary circumstances?

24. State the objections against the party polarity system as shown in Fig. 172.

25. What are the advantages of the harmonic party-line system?

26. To how many frequencies is the harmonic system usually limited?

27. What can you say about the commercial success of the step-by-step method?

28. State the principles of a lock-out party line.

29. For what purpose is a condenser placed in the receiver circuit of each station in the K.B. lock-out system?

30. How are the selecting relays in Roberts line restored to their normal position after a conversation is finished?

31. What are the objections against the Roberts system?

REVIEW QUESTIONS

ON THE SUBJECT OF TELEPHONY

PAGES 287--315

* * * * *

1. What are electrical hazards?

2. When is the lightning hazard least?

3. What actions can electricity produce? Which involves the greater hazard to the value of property?

4. When is a piece of apparatus called "self-protecting"?

5. Why must a protector for telephone apparatus work more quickly for a large current than for a small one?

6. State the general problem which heating hazards present with relation to telephone apparatus.

7. What is the most nearly universal electrical hazard?

8. Sketch and describe the saw-tooth lightning arrester.

9. Make diagram of the carbon-block arrester and state its advantages.

10. Describe a vacuum arrester.

11. Explain the reason for placing an impedance in connection with the lightning arrester.

12. What is the purpose of the globule of low-melting alloy in the Western Electric Company's arrester?

13. Why are not fuses good lightning arresters?

14. What is the proper function of a fuse?

15. Make sketch of a mica slip fuse.

16. Define _sneak currents_.

17. Make a diagram of a sneak-current arrester and describe its principles and working.

18. Describe a heat coil.

19. Sketch a complete line protection.

20. Where is the proper position of the fuse?

21. Which wires are considered exposed and which unexposed?

22. Why is it not necessary to install sneak-current arresters in central-battery subscribers' stations?

23. Sketch and describe the action of a combined sneak-current and air-gap arrester, as widely used by Bell companies.

24. Describe the self-soldering heat-coil arrester.

25. What is the purpose of ribbon fuses?

26. What is a drainage coil?

REVIEW QUESTIONS

ON THE SUBJECT OF TELEPHONY

PAGES 317--386

* * * * *

1. What is a central office?

2. What are (_a_) subscriber's lines? (_b_) Trunk lines? (_c_) Toll lines?

3. For what purpose is the switchboard?

4. Give short descriptions of the different classes of switchboards.

5. How are manual switchboards subdivided? Describe briefly the different types.

6. Define A and B boards.

7. What is a call circuit?

8. What kind of calls are handled on a toll switchboard?

9. Give drop symbol and describe its principles.

10. What is a jack?

11. Make a sketch of a plug inserted into a jack.

12. Give jack and plug symbols.

13. What are ringing and listening keys?

14. Show symbols for ringing and listening keys.

15. State the parts of which a cord equipment consists.

16. Show step by step the various operations of a telephone system wherein the lines center in a magneto switchboard. Make all the necessary diagrams and give brief descriptions to show that you understand each operation.

17. On what principle does a drop with night-alarm contact operate?

18. What is the advantage of associating jacks and drops?

19. Describe the mechanical restoration as employed in the Miller drop and jack.

20. Describe the electrical restoration of drop shutters as manufactured by the Western Electric Company.

21. What complications arise in ringing of party lines and how are they overcome?

22. Give diagram of the complete circuit of a simple magneto switchboard.

23. Sketch night-alarm circuit with relay.

24. What is a convertible cord circuit?

25. State what disadvantages may be encountered under certain conditions with a bridging drop-cord circuit.

26. Are lamps in cord circuits to be advocated on magneto switchboards?

27. What is the function of the cabinet?

28. Give cross-section of upright switchboard as used in the magneto system.

29. What is the purpose of a sectional switchboard?

30. Give a short description of the essential parts of a sectional switchboard.

INDEX

INDEX

_The page numbers of this volume will be found at the bottom of the pages; the numbers at the top refer only to the section._

A

Acousticon transmitter
Acoustics
characteristics of sound
loudness
pitch
timbre
human ear
human voice
propagation of sound
Air-gap vs. fuse arresters
Amalgamated zincs
Arrester separators
Audible signals
magneto bell
telegraph sounder
telephone receiver
vibrating bell
Automatic Electric Company
direct-current receiver
transmitter
Automatic shunt

B

Bar electromagnet Battery bell Battery symbols Blake single electrode Brazed bell Broken-back ringer Broken-line method of selective signaling

C

Capacity reactance
Carbon
adaptability
limitations
preparation of
superiority
Carbon air-gap arrester
Carbon-block arrester
Carrying capacity of transmitter
Central-office protectors
Characteristics of sound
loudness
pitch
timbre
Chloride of silver cell
Closed-circuit cells
Closed-circuit impedance coil
Common-battery telephone sets
Condensers
capacity
charge
conventional symbols
definition of
dielectric
dielectric materials
functions
means for assorting current
sizes
theory
Conductivity of conductors
Conductors, conductivity of
Conventional symbols
Cook
air-gap arrester
arrester
arrester for magneto stations
Crowfoot cell
Current supply to transmitters
common battery
advantages
bell substation arrangement
bridging battery with impedance coils
bridging battery with repeating coil
current supply from distant point
current supply over limbs of line in parallel
Dean substation arrangement
double battery with impedance coil
Kellogg substation arrangement
North Electric Company system
series battery
series substation arrangement
Stromberg-Carlson system
supply many lines from common source
repeating coil
retardation coil
local battery

D

Dean
drop and jack
receiver
wall telephone hook
Desk stand hooks
Kellogg
Western Electric
Dielectric
Dielectric materials
dry paper
mica
Differential electromagnet
Direct-current receiver
Drainage coils

E

Electric lamp signal
Electrical hazards
Electrical reproduction of speech
carbon
conversion from sound waves to vibration of diaphragm
conversion from vibration to voice currents
conversion from voice currents to vibration
cycle of conversion
detrimental effects of capacity
early conceptions
electrostatic telephone
induction coil
limitations of magneto transmitter
loose contact principle
magneto telephone
measurements of telephone currents
variation of electrical pressure
variation of resistance
Electrical signals
audible
magneto-bell
telegraph sounder
telephone receiver
vibrating bell
visible
electric lamp signal
electromagnetic signal
Electrodes
arrangement of
carbon preparation
multiple
single
Electrolysis
Electromagnetic method of measuring telephone currents
Electromagnetic signal
Electromagnets and inductive coils
conventional symbols
differential electromagnet
direction of armature motion
direction of lines of force
electromagnets
low-resistance circuits
horseshoe form
iron-clad form
special horseshoe form
impedance coils
kind of iron
number of turns
types
closed-circuit
open-circuit
toroidal
induction coil
current and voltage ratios
design
functions
use and advantage
magnet wire
enamel
silk and cotton insulation
space utilization
wire gauges
magnetic flux
magnetization curves
magnetizing force
mechanical details
permeability
reluctance
repeating coil
winding methods
winding calculations
winding data
winding terminals
Electrostatic capacity
unit of
Electrostatic telephone
Enamel

F

Five-bar generator Fuller cell

G

Galvani Generator armature Generator cut-in switch Generator shunt switch Generator symbols Granular carbon Gravity cell

H

Hand receivers
Harmonic method of selective signaling
advantages
circuits
in-tune system
limitations
principles
tuning
under-tune system
Head receivers
Heat coil
Holtzer-Cabot arrester
Hook switch
automatic operation
contact material
design
desk stand hooks
Kellogg
Western Electric
purpose
symbols
wall telephone hooks
Dean
Kellogg
Western Electric
Horseshoe electromagnet
Human ear
Human voice

I

Impedance coils
kind of iron
number of turns
symbols of
types
closed-circuit
open-circuit
toroidal
Inductance vs. capacity
Induction coil
current and voltage ratios
design
functions
use and advantage
Inductive neutrality
Inductive reactance
Insulation of conductors
Introduction to telephony
Iron-clad electromagnet
Iron wire ballast

K

Kellogg
air-gap arrester
desk stand hook
drop and jack
receiver
ringer
transmitter
wall telephone hook

L

Lalande cell Lamp filament Le Clanché cell Lenz law Line signals Lines of force, direction of Loading coils Lock-out party-line systems broken-line method operation Poole system step-by-step system Loudness of sound Low-reluctance circuits horseshoe form iron-clad form

M

Magnetic flux
Magnetization curves
Magnetizing force
Magneto bell
Magneto operator
Magneto signaling apparatus
armature
automatic shunt
battery bell
generator symbols
magneto bell
magneto generator
method of signaling
polarized ringer
pulsating current
ringer symbols
theory
Magneto switchboard
automatic restoration
mechanical
Dean type
Kellogg type
Monarch type
Western Electric type
circuits of complete switchboard
code signaling
commercial types of drops and jacks
early drops
jack mounting
manual vs. automatic restoration
methods of associating
night alarm
tubular drops
component parts
jacks and plugs
keys
line and cord equipments
line signal
operators' equipment
cord-circuit considerations
double clearing-out type
lamp-signal type
non-ring through type
series drop type
simple bridging drop type
definitions
electrical restoration
grounded and metallic-circuit lines
mode of operation
night-alarm circuits
operation in detail
clearing out
essentials of operation
normal condition of line
operator answering
operator calling
subscriber calling
subscribers conversing
operator's telephone equipment
cut-in jack
ringing and listening keys
horizontal spring type
party-line ringing keys
self-indicating keys
vertical spring type
switchboard assembly
functions of cabinet
sectional switchboards
upright type of switchboard
wall type switchboard
switchboard cords
concentric conductors
parallel tinsel conductors
steel spiral conductors
switchboard plugs
Magneto telephone
Magneto telephone sets
Mica card resistance
Mica slip fuse
Microtelephone set
Monarch drop and jack
Monarch receiver
Monarch transmitter
Multiple electrode
Mutual induction

N

Non-inductive resistance devices
inductive neutrality
provisions against heating
temperature coefficient
types
differentially-wound unit
iron wire ballast
lamp filament
mica card unit
Non-selective party-line systems
bridging
limitations
series
signal code

O

Open-circuit cells Open-circuit impedance coil Operator's receiver

P

Packing of transmitters
Permeability
Pitch
Doppler's principle
vibration of diaphragms
Polarity method of selective signaling
Polarization of cells
Polarized ringer
brazed bell
Kellogg
Western Electric
Poole lock-out system
Primary cells
conventional symbol
series and multiple connections
simple voltaic
types of
closed-circuit
Fuller
gravity
Lalande
prevention of creeping
setting up
open-circuit
Le Clanché
standard
chloride of silver
Propagation of sound
Protective means
against high potentials
air-gap arrester
advantages of carbon
commercial types
continuous arcs
discharge across gaps
dust between carbons
introduction of impedance
metallic electrodes
vacuum arresters
against sneak currents
heat coil
sneak-current arresters
against strong currents
fuses
enclosed
mica
proper functions
central-office protectors
self-soldering heat coils
sneak-current and air-gap arrester
city exchange requirements
complete line protection
electrolysis
subscribers' station protectors
ribbon fuses
Pulsating-current commutator

R

Receivers
Dean
direct-current
early
Kellogg
modern
Monarch
operator's
single-pole
symbols
Western Electric
Reluctance
Repeating coil
Ribbon fuses
Ringer symbols
Ringing and listening key
Robert's latching relay
Robert's self-cleansing arrester
Rolled condenser

S

Saw-tooth arrester
Selective party-line systems
broken-line method
classification
broken-line systems
harmonic systems
polarity systems
step-by-step systems
harmonic method
polarity method
step-by-step method
Self-induction
Signal code
Signaling, method of
Silk and cotton insulation
Single electrode
Single-pole receiver
Sneak-current arresters
Solid-back transmitter
Sound
characteristics of
loudness
pitch
timbre
Standard cell
Step-by-step lock-out system
Step-by-step method of selective signaling
Subscribers' station protectors
Switchboard cords
Switchboard plugs
Switchboard transmitter
Symbols
battery
condenser
generator
hook switch
impedance coil
induction coil
receiver
repeating coil
ringer
ringing and listening key
transmitter

T

Table
condenser data
copper wire
German silver wire--18 per cent
German silver wire--30 per cent
metals, behavior of, in different electrolysis
signal code
specific inductive capacities
temperature coefficients
transmission distances, limiting
winding data for insulating wires
Tandem differential electromagnet
Telegraph sounder
Telephone currents, measurements of
electromagnetic method
thermal method
Telephone exchange, features of
districts
subscribers' lines
switchboards
toll lines
trunk lines
Telephone lines
conductivity of conductors
electrostatic capacity
inductance of circuit
inductance vs. capacity
insulation of conductors
transmission
Telephone sets
classification of
common-battery telephone
magneto telephone
wall and desk telephones
common-battery
desk
hotel
wall
magneto
circuits of
bridging
series
desk
wall
Temperature coefficients
Thermal method of measuring telephone currents
Timbre
Toroidal impedance coil
Toroidal repeating coil
Transmission, ways of improving
Transmitters
acousticon
Automatic Electric Company
carrying capacity
conventional diagram
electrode
arrangement of
multiple
single
granular carbon
Kellogg
materials
Monarch
packing
sensitiveness
switchboard
symbols
variable resistance
Western Electric solid-back

U

Under-tuned ringer

V

Vacuum arrester
Variable resistance
Vibrating bell
Visible signals
electric lamp
electromagnetic
Volta
Voltaic cell
amalgamated zincs
difference of potential
local action
polarization
theory

W

Wall telephone hooks
Dean
Kellogg
Western Electric
Western Electric
air-gap arrester
desk stand hook
drop and jack
receiver
ringer
solid-back transmitter
station arrester
wall telephone hook
White transmitter
Wire gauges