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TEL/40T or SONIC 70

GEC Sonic 70 overview

The Sonic 70, launched in April 1966, was yet another attempt to simplify the design of the Telephone 706, at the same time modernising the shape of the telephone a little and adding the contrast of an aluminium front lip. A single-coil ringer was fitted, with an optional loudness control, and the cradle plungers were made of Delrin plastic. A hand hold was provided at the rear of the instrument to make it easier to carry.

Two-tone green, two-tone grey, black and white.

None known. The product appears to have been a failure.

Brochure photograph.

Catalogue Number

See also TEL/42T/ATT

Telephone by G.E.C.

The Sonic 70 has been designed specifically for the Administration that requires a simple efficient telephone. Market research has shown that current telephones embody many facilities which are seldom used; this fact has greatly influenced the designers of the Sonic 70 and the result is an efficient single-subscriber instrument at low cost.

The basic high-quality performance and reliability that have made G.E.C. telephones acceptable to Administrations throughout the world, are retained. The transmitter,  receiver and dial are the same components that have proved themselves in many millions of telephones already in service.

The case is moulded in scratch-resistant plastic that withstands rigorous use in climatic extremes. Special attention has been given to ensure that when the handset is replaced, it will
always 'walk' into the correct rest position. A hand hold is moulded into the rear of the case to facilitate carrying the complete instrument. The simple contemporary lines of the new design minimize dust collection.

The handset, moulded in the same material as the case, is light in weight and combines a high degree of user comfort with maximum transmitter efficiency. Its shape ensures that, with the receiver held to the ear normally, the transmitter is located in the most efficient position.

The carbon-granule transmitter and the rocking-armature receiver provide clear speech reproduction with low distortion over a wide speech-frequency range.

For the convenience of the user, alternative lead-out points for the handset cord are Handset cord location located at either side of the telephone base.

Either the G.E.C. articulated-trigger dial or the new G.E.C. moulded-plastic dial is available for use in this telephone and is recessed into the case. The dial is connected to the base terminations by a cable form long enough to facilitate maintenance.

The finger plate is made of transparent plastic, so that the figures can be viewed through it and are always visible; thus, the risk of dialling error is minimized. A wide range of number rings is available to suit the requirements of individual Administrations.

Cradle Switch
The cradle switch springset is operated by "Delrin" plungers. It is assembled on the case and connected to the other components by the same cable form that connects the dial.

The single-coil ringer has a pleasant purposeful sound and will operate from all normal exchange ringing supplies. A bell volume control can be fitted if required.

The cords are P.V.C. sheathed, affording protection to the conductors against wear and condensation. All cord ends are firmly secured so that the terminations are not subject to stresses. The colour of the cords match that of the telephone.

Special insulation is included so that the telephone can be used in any climate. The design provides both adequate ventilation against humidity and protection against the ingress of insects.


Abridged Specification

Catalogue Number

Case and handset moulded in A.B.S. high-impact plastic. Four colours available: black, dual green, dual grey, and white.

PVC-covered cadmium-tinsel-conductor cords, colour to match telephone. Held in position by grommets which relieve conductors of any stresses.
Line cord: straight, 135 cm (54 in).
Handset cord: coiled, 25 cm (10 in) unextended; 170 cm (68 in) extended.

Articulated trigger type speed: 10 p.p.s.
Break-to-make ratio: 2 to 1.

Moulded plastic type speed: 10 p.p.s. or 20 p.p.s.
break-to-make ratio: 2 to 1.
can be varied to suit the Administration.

Single coil, d.c. resistance 1250 Ohms.
Impedance 20000 at 25 c/s, 220000 at 1000 c s.
Accepts ringing current supplies of between 16 and 30 c/s. Double gong, harmonizing tones.

Suitable for use in all climates. Prevents entry of insects.

Complete telephone: 1 kg (3 lb). Handset: 280 gm (10 oz).

Taken from the GEC Catalogue Leaflet STL22A


Dated 1966



Tel 40 production line at the Aycliffe Works


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Last revised: October 14, 2022