COILS, INDUCTION

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 Magneto and 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Superseded by the Coil, Induction No. 12.

This induction coil was known as a self connecting type, because the fixing screws form part of the electrical connection to the apparatus wiring.  The four screws fix to threaded wire tags which are connections to the apparatus wiring.

Click here for more information
 

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.
 

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Superseded by Coil, Induction No. 14.

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Superseded by Coil, Induction No. 14.

Induction Coil used for vacuum protector testing.

Primary winding - 0.15 Ohms.
Secondary winding - 350 Ohms.

With trembler break and 0.02uf condenser.
 

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.
 

Two windings of 17 Ohms and 26 Ohms.

Used on Supervisors Circuits and the Telephone No. 49 (Glasgow and Brighton telephones).

.
 

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 non-induction 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.

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.

Two winding Induction Coil used on the Telephone No. 44.

Primary winding is 1.7 Ohms and secondary winding is 75 Ohms.

Drawing - 8841 (Mark 235).

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 non-induction resistance in series of 360 ohms.

Operators circuit on CB No. 1 exchanges.

Superseded by Coil, Induction No. 8.

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.

Click here for more information

Drawing - 62203 (Mark 235).
 

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.

Click here for more information

Drawing - 10019.

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
 

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.
 

Induction Coil with two windings of 17 Ohms (1700 turns) (tags 1 & 2) and 33 Ohms (1400 turns) (tags 3 & 4).

Used with Anti-sidetone 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.

Dimensions are 102mm x 27mm x 24mm.

Siemens Brothers called this their Coil, Induction No. 18A.
 

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).

Dimensions are 87mm x 24mm x 24mm.

Siemens Brothers called this their Coil, 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.

Dimensions are 102mm x 27mm x 24mm.

Siemens Brothers called this their Coil, Induction No. 31A.

Ericsson Part No. N3529 & N3529A.

STC Part No. 5011.
.

Three windings of 50 Ohms (tags 3 & 4), 215 Ohms (tags 3 & 6) and 17 Ohms (tags 1 & 2).

It also has two non-inductive resistances of 150 Ohms (tags 3 & 7) and 400 Ohms (tags 3 & 5).

Specification - D1033.
Drawing - 9875.

Click here for more information
 

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 non-inductive resistances of 150 Ohms (tags 3 & 5 with 415 Ohm winding in series), 50 Ohms (tags 5 & 6) and 150 Ohms (tags 3 & 7).

Click here for more information

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.
 

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.

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.

Five windings of 16 Ohms, 8 Ohms, 35 Ohms, 30 Ohms (NI) and 30 Ohms (NI).

Click here for further information

ETL Part N3520.

Drawing - 62207.

Dimensions are 92mm x 28mm x 24mm.

Siemens Brothers called this their Coil, Induction No. 33A.

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.
 

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.

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.

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.