GEC K 25

K 25

BATTERY WALL TELEPHONES

Wall pattern telephone with "Byng" Transmitter.

Price in 1907 - £1.2.6.

Taken from a G.E.C. Telephone Catalogue (1907)

Wiring two Telephones together

Each telephone requires three 1.5 volt batteries.  The phones are normally connected together by two wires, but if the ZE terminal is connected to a good earth then only the L terminals are connected together with one wire.  It is recommended to use two wires and dispense with the earth connection.

At each telephone connect the batteries as follows:-

1. Connect the three batteries in series.
2. Connect the free negative terminal of the battery set to terminal ZE on the phone.
3. Connect the free positive terminal of the battery set to terminal C on the phone.
4. Connect the positive terminal of the centre battery to terminal MC on the phone.

Connect the two phones together as follows:-

1. Connect terminal ZE of one phone to terminal ZE of the other.
2. Connect terminal L of one phone to terminal L of the other.

Wiring diagram

In the diagram the following abbreviations are:-

C = Carbon (Positive terminal of battery).
Z = Zinc (Casing and negative of battery).
MC = Microphone Carbon.
L = Line.
ZE = Zinc earth (this is connected to earth if only one line wire is used to connect the telephones together.  If two line wires are used then just connect the second wire to ZE and ZE).

Last revised: July 30, 2025