GEC K7820 & K7826

K7820

BATTERY CALL
SUPERIOR QUALITY
(With Induction Coil)
The Hunningscone-Deckert Wall Telephone

This well known Instrument ranks as the pioneer of Battery Ringing Telephones. It still maintains it's position as the most satisfactory Battery Call Telephone set at a moderate price.

It consists of Hunningscone-Deckert Granular Transmitter, Induction Coil, Double Pole Watch Receiver, Call Bell, Ringing key and Automatic Switch Hook. Wood work of solid well seasoned Polished Walnut and all exterior Metal parts Nickel plated.

Can be used on lines up to half a mile in length.

Price in 1908 was £1.7.6.

Taken from the GEC Telephone Catalogue, K Section, 10th Edition, 1908


1926 model	1932 model

K7820

Battery Call Telephone

Similar to K7805 but fitted with Hunningscone-Deckert transmitter.

This instrument is constructed of polished walnut and the finish of all external metal work is oxidised.

Cost in 1916 was £1.10.0
Cost in 1926 was £3.1.9
Cost in 1932 and 1935 was £2.7.6

Later version had a carbon granule transmitter and the terminals were internal.

Wall pattern battery call telephone, comprising K 7670 carbon granule transmitter, K 7630 'Watch' pattern double-pole receiver, K 7728 induction coil, automatic switch hook, ringing key and 25 ohm bell on tail piece.

Weight, 3 lbs. 8 ozs.

Dimensions, l0 x 7 x 5 ins.

In 1916 the telephone could be supplied mounted on a backboard. See K7825.

BATTERY CALL TELEPHONES WITH INDUCTION COIL

Cabinet work of well seasoned walnut; external metal parts oxidised copper bronze.
The telephone instruments described here, along with K 7847, K 7851 & K 7855 can be used together for the following requirements:-

Connected up in pairs, to ring and speak both ways over approximately half a mile, a double line or single line with earth return.

To connect up three stations by the use of a K 8500 switch and a K 8313 bell, to enable 'A' station to ring and speak both ways to 'B' and 'C' stations only; the latter cannot communicate with each other.

To connect up three stations by the use of a K 8510 switch and a K 8313 bell to enable 'A' station to ring and speak both ways to 'B' and 'C' stations, and the later stations to speak together by 'A' station placing the K 8510 switch in the through position.

Where a number of telephones are required in a building, these telephones can be installed to work in conjunction with Battery Call Switchboards K 8335, K 8350 and K 8360 with an operator in attendance.

Found in the 1916, 1926, 1932 and 1935 Catalogues

K 7826
Backboard only, with battery box to accommodate three No. 3 G.E.C. dry cells, with space for mounting a K 7820 telephone.

Weight, 3 lbs. 4 ozs.
Dimensions, 20 x 9 x 4.5 ins.

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:-

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

Connect the two phones together as follows:-

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

In the diagrams below 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).

Click here for additional wiring diagrams

Circuit Diagram