Coils Induction No.
1 Two windings of 1 Ohm (silk covered copper wire of 25 mils) and
25 Ohms (11 mils). The cores are a 9/32 inch bundle, No. 24 S.W.G.
well annealed, charcoal iron, left black from the annealing process to
prevent eddy currents.
Used on local battery circuits and was a self connecting type.
The National Telephone Company also produced a similar Induction Coil
with the 1 ohm winding of 20.5 mils and the 25 ohm winding of 10.75
mils. The core was a bundle of 22 mil wire of 5/16" diameter each.
Superseded by the Coil, Induction No. 12.
Known as a self connecting type, because the fixing screws form part of the electrical connection to the
apparatus as they fix into to threaded terminals, that are the
connections to the external wiring.
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Coils Induction No.
2 Two windings of 1 Ohm (silk covered copper wire of 25 mils) and
150 Ohms (7 mils). The cores are a 9/32 inch bundle, No. 24 S.W.G.
well annealed, charcoal iron, left black from the annealing process to
prevent eddy currents.
Used on the Telephone No. 108 and certain switchboards on local battery circuits.


Coils Induction No. 3 Two winding
coil with soldered tags on the outer sides of the coil cheeks.
Inner winding is 26 Ohms (tags 3 and 4) and outer winding is 17 Ohms (tags
1 and 2).
Used on Instrument, Subscribers, Wall, NT No. 13, Switchboards and the
Bellset No. 1.
Superseded by Coil, Induction No. 14.


Coils Induction No.
4 Two winding coil  self connecting type.
Inner winding 26 Ohms (tags 3 & 4) and outer winding 17 Ohms (tags 1
& 2).
Used on Telephone No. 1 (Mark 234) and Bellset No. 1A (Mark 234).
Superseded by Coil, Induction No. 14.


Coils Induction No.
5 Induction Coil used for vacuum protector testing.
Primary winding  0.15 Ohms.
Secondary winding  350 Ohms.
With trembler break and 0.02uf condenser.


Coils Induction No. 6 Rectangular in construction and
consisting of two windings, this Induction Coil was used on Operators C.B. systems.
Coil
Primary winding  11 ohms (tags 5 & 6).
1st Secondary winding  58 ohms (tags 3 & 4).
2nd Secondary winding  240 ohms (tags 5 & 6).
Dimensions of base are 7.1 in x 2 in.


Coils Induction No.
7 Two windings of 17 Ohms and 26 Ohms.
Used on Supervisors Circuits and the Telephone No. 49 (Glasgow and
Brighton telephones).
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Coils Induction No.
8 Two windings on a brass frame with black rectangular metal cover.
8 tags.
1st coil  Primary winding 18 Ohms and secondary winding 130 Ohms.
2nd coil  Primary winding 18 Ohms and secondary winding 130 Ohms with a
360 Ohm noninduction in series.
Used on the operators circuit on CB No. 1 and 10 exchanges.
Supersedes Coil, Induction No.11.
Drawing  8156 & 62206.
Ericsson Part No. N3506.


Coils Induction No.
9 Two winding coil with black cover.
Primary winding 17 Ohms (tags 1 & 2) and secondary winding 26 Ohms (tags 3 & 4).
Used on Supervisors Circuits on CB No. 1 and 10 exchanges.
Mounts on Drilling No. 92.
Drawing  NT8452.
Ericsson Part No. N3505.


Coils Induction No.
10 Two winding Induction Coil used on Telephone No. 44.
Primary winding is 1.7 Ohms and secondary winding is 75 Ohms.
Drawing  8841 (Mark 235).


Coils Induction No.
11 Two windings on a brass frame with metal cover. 5
tags.
1st coil  Primary winding is 18 Ohms and the secondary winding is 130 Ohms.
2nd coil  Primary winding 18 Ohms and secondary winding 130 Ohms with a
noninduction resistance in series of 360 ohms.
Operators circuit on CB No. 1 exchanges.
Superseded by Coil, Induction No. 8.


Coils Induction No. 12 Two windings
Induction Coil with soldered tags.
Primary winding is 1 Ohm (tags 1 & 2) and the secondary winding
is 25 Ohms (tags 3 & 4).
Standard for L.B. system telephone and switchboards.
Superseded Coils Induction No. 1 or NT No. 12.
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Drawing  62203 (Mark 235).


Coils Induction No. 13 

Coils Induction No. 14
Induction Coil with two windings of 26 Ohms (1400 turns) (tags 3 & 4
 inner) and 17 Ohms (1700
turns) (tags 1 & 2  outer).
Superseded Coils Induction No's 3 and 4.
Used on the Bellset No. 1 and Telephone No, 125.
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Drawing  10019.


Coils Induction No. 15
Induction Coil with three windings and six connection tags.
Primary winding is 400 turns of No. 23 SWG at a resistance of 1 Ohm (tags 1 & 2), 1st secondary winding
is 1000 turns of 32 SWG at a resistance of 19 Ohms (tags 3 & 4) and
second secondary of 1500 turns of 32 SWG at a resistance of 38 Ohms (tags 5 & 6).
Used on L.B. Telephones on long lines and the Bellset No. 21


Coils Induction No. 16
Metal cased (tinplate), three winding
Induction Coil with 6 connector tags.
Primary winding 4 Ohm, 1st secondary winding 20 Ohms and second secondary
winding of 440 Ohms.
Used on operators telephone circuits on C.B. switchboards.
Drawing  9896 (casing).
Ericsson Part No. N3532.


Coils Induction No. 18
Induction Coil with two windings of 17 Ohms (1700 turns) (tags 1 & 2) and 33 Ohms (1400
turns) (tags 3 & 4).
Used with Antisidetone Transformer No. 35A.
A No. 18A was a No. 18 complete with two mounting brackets.
Was the N.T. No. 4.
Drawing  9875.
Specification  D862.


Coils Induction No. 20
Three windings of 30 Ohms (1600 turns) (tags 4 & 5), 200 Ohms (1580 turns)
(tags 3 & 5) and 44 Ohms (2400 turns) (tags 1 & 2).
Also two non inductive resistances of 30 Ohms (tags 3 & 6) and 85
Ohms (tags 2 & 5). Siemens Brothers called this the Induction Coil No. 21.


Coils Induction No. 21
Used in Local Battery situations.
Three windings of 1 Ohm (400 turns) (tags 1 & 2), 17 Ohms (1000
turns) (tags 3 & 4) and 33 Ohms (1500 turns) (tags 5 & 6).
Used on Telephone No's 250 & 251 and Bellset No's 21, 31 and 37.
A No. 21A was a No. 21 complete with two mounting brackets.
In Australia some 300 series magneto phones used the No. 21A as
follows (no winding details):
1 Ohm between tags 1 & 2 .
17 Ohms between tags 3 & 4.
33 Ohms + 900 Ohms NI between tags 5 & 6
tags 3 & 5 linked.
Specification  D980.
Drawing  9875.
Ericsson Part No. N3529 & N3529A.
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Coils Induction No. 22
Mark 1 Three windings of 50 Ohms (tags 3 & 4), 215 Ohms
(tags 3 & 6) and 17 Ohms
(tags 1 & 2).
It also has two noninductive resistances of 150 Ohms (tags 3 & 7) and
400 Ohms (tags 3 & 5). Specification  D1033.
Drawing  9875. Click here for more information


Coils Induction No. 22
Mark 2 Three windings of 54 Ohms (1600 turns) (tags 3 & 4), 415 Ohms (2000 turns)
with 150 Ohm NI resistance in series (tags 3 & 5) and 17 Ohms (2000 turns)
(tags 1 & 2).
It also has three noninductive resistances of 150 Ohms (tags 3 & 5 with
415 Ohm winding in series), 50 Ohms (tags 5 & 6) and 150 Ohms (tags 3 & 7).
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Coils Induction No. 23
Three windings of 44 Ohms (tags 1 & 2), 30 Ohms (tags 4 & 5) and
200 Ohms (tags 3 & 5). A NI resistor of 85 Ohms is between tags 2
and 5.


Coils Induction No. 24
Three windings of 83 Ohms (1600 turns) (tags 3 & 4), 550 Ohms
(2000 turns) (tags 3 & 5) and 21 Ohms (2000 turns) (tags 1
& 2).
Also has two non inductive resistances of 50 Ohms (tags 5 & 6)
and 150 Ohms (tags 3 and 7). Drawing  62201.


Coils Induction No. 25
Two windings of 25 Ohms (tags 3 & 4) and 1 Ohm (tags 1 & 2).


Coils Induction No. 27
An Induction Coil used on many GPO telephones.
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information
ETL Part N3520.
Drawing  62207.


Coils Induction No. 29 Two windings of
36 Ohms (600 turns) (tags 2 & 3) and 135 Ohms (2700 turns) (tags 1 & 2).
Used on Telephone No. 280.
Drawing  90719.


Coils Induction No. 30
Three windings of 15 Ohms (1220 turns), 10.5 Ohms (666 turns) and 7.5
Ohms (420 turns). Used on the experimental Telephone No. 700.


Coils Induction No. 31
Three windings of 6 Ohms (315 turns) (tags 2 & 3), 8 Ohms (540
turns) (tags 1 & 2) and 22 Ohms (900 turns) (tags 4 & 5). Used
on Telephone No's 706, 710 and 711. Drawing  61271.


Coil Induction No. 32
Three windings of 7 Ohms (235 turns) (tags 2 & 3), 11 Ohms (402
turns) (tags 1 & 2) and 23 Ohms (670 turns) (tags 4 & 5). Used
on Telephone No's 722, 740, 741 and 746. Drawing 
92682.

