Great War Telephone Equipment 1914-1918:

Telephone sets Portable C Mk 1

The Telephone set Portable C Mk 1 consists of a box containing two dry cells, a magneto generator, polarised bell, induction coil testing plug, and a "Hand Telephone C Mk.1."

The cells are joined in series, and fit one in each corner at the back of the box. the pressel switch of the hand telephone has an up and down contact, that is, it makes a contact in the released as well as the depressed position. The generator handle and testing plug are carried, when not in use, by holders inside the lid. The telephone is provided with three terminals, two for the line wires and one for the earth connection of the lightening discharger. This is of the serrated plate type.

The generator, receiver, secondary of induction coil and bell are all connected in series; but to reduce the resistance of the incoming call circuit, all except the  bell are normally short-circuited. The secondary winding of the induction coil and the receiver are short-circuited by the pressel switch in its up position, the generator by a cut-out.

Telephone sets Portable C Mk 2 (Great War)

C Mk 2 (Folded)

C Mk 2 (Open)

C Mk 2 (Ready for use)

Telephone sets Portable C Mk 2

This set was introduced as an improvement on the C Mk. 1, and is now the standard magneto-ringing telephone set in service. The generator, magneto bell, and secondary speaking circuits are all connected in parallel,  but to ensure that any incoming ringing current shall all pass through the bell, the generator and speaking circuits are normally disconnected. The generator is disconnected by an automatic cut-out device, the speaking circuit at the pressel switch of the hand telephone, which is of the C Mk.III type.

The set is protected from lightening by bobbin dischargers and a serrated plate discharger in each line. There are three terminals, L1 and L2, which are the terminals of the telephone set, and E which goes to the earth plate of  the lightening discharger only. Hence when working with a metallic circuit the two lines go to L1 and L2, whilst E is connected to earth. If an earth return is used, L1 goes to line, whilst L2 and E are strapped together and connected to earth.

The box opens at the two ends. The front which is held by a hook only, gives access to the line terminals, the hand telephone, the lightening dischargers, and the generator handle. The back held by screws, admits of the removal of the battery and a tray, which latter carries the generator, bell and induction coil.

Telephone sets Type 100A (Mark 234).     1918

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Telephone sets Type 110 (Mark 234).     1918 G.P.O. Model.

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