GEC
TEL/1T and TEL/2T

The high performance is the result of new components in a new circuit. The receiver is of the rocking-armature type, with a substantially flat frequency response and an output l0dB better than its predecessors. A new induction coil transfers some of this gain to the sending side, where it is added to the gain that results from a new shape of handset.

The consequent overall performance makes the new telephone so much better than earlier models that longer lines or smaller conductors in local distribution networks become practicable.

"G.E.C. 1000" TELEPHONE
The gentle curved lines of the "G.E.C. 1000" Telephone, the most recent design, harmonise with modern schemes of decoration, whilst retaining the dignity required for office furniture.

Finger tip grips for lifting the set with ease are provided by two inserts in the sides of the case near the top, one on each side. In telephones for tropical countries these inserts serve a double purpose; they are pierced, and, together with small holes in the bottom of the instrument, permit air to circulate freely in the instrument, thereby reducing internal condensation.

All components, except the dial, are mounted on a single baseplate, where all are easily accessible for maintenance.

HANDSET
The redesigned handset improves the overall performance, and affords greater comfort to the user. The increased curvature tilts the transmitter inset into a more sensitive position for normal use, resulting in an improvement of about 2dB in sending performance and an overall improvement in the frequency response.

TEL/1P/ATS

DIAL
The automatic telephones are fitted with the well-known G.E.C. trigger-type dial, standardised by many Overseas Administrations and the British Post Office. The dial operates at 10 impulses per second, and has a break to make ratio of 2:1. Dials having other ratios can be fitted if required.

For very dusty atmospheres, a transparent plastic cover can be fitted to the back of the dial to give complete enclosure of the mechanism.

In manual telephones the dial is replaced by a dial dummy. The telephones are simply converted for automatic working by replacing the dial dummy by a dial, and connecting it to the terminals in the telephone by a dial cord.

TRANSMITTER
The transmitter is of the immersed-electrode, carbon-granule, capsule type. Its good frequency response and power output have contributed notably to the performance of G.E.C. telephones in the past, while its reliability has been proved in service in temperate and tropical climates.

RECEIVER
The receiver is of the new rocking-armature capsule type, and has a very-high electro-acoustic conversion ratio. Acoustic equalisation produces an improved frequency response. The light alloy diaphragm increases the ratio of effective area to effective mass. The magnet is stabilised during manufacture so that it has optimum strength.

The whole improvement gained by the use of this receiver is not needed on the receiving side; in consequence, a new induction coil is included to transfer some of the improvement to the sending side.

SIDETONE
In effecting the transfer of gain from receiving to sending side, the highest practicable degree of sidetone suppression has been maintained. The circuit is designed to give maximum suppression of sidetone on reactive lines (i.e. cable pairs) because the vast majority of telephones are connected to their exchanges by cable.

RINGER
The ringer has a resistance of 1000 ohms and an impedance of 17000 ohms at 1000c/s. It responds to alternating ringing current from hand or automatic ringing machines. Coils of higher impedance for multi-party working are fitted when required.

CRADLE SWITCH
The cradle switch has been designed to eliminate any likelihood of sticking plungers. Twin contacts give maximum reliability and the springsets are mounted so that any accumulation of dust tends to fall away.

TROPICALISATION
The three G.E.C. features, special insulation, ventilation, and protection against humidity and insects, are incorporated in all telephones supplied to tropical areas.

Some Overseas Administrations have found that a longer noise-free life for the transmitter is obtained in their areas when a direct current path shunts the transmitter. When specified on orders, this protection is provided by connecting a 300-ohm resistor across the transmitter at the telephone's internal terminal strip. The sending performance of the instrument is reduced by less than 2dB, and the effect on the receiving performance is negligible.

COLOUR
In addition to the normal black instrument, a range of two-tone telephones can be supplied in which the case is coloured, and all other parts, including the dial, are black. The range of colours is ivory, red and green. The two-tone telephones have the following advantages over all-colour telephones:-

Delicate and pleasing shades can be used since the difficulty of shade matching is eliminated.

HANDSET COMFORT
Many tests have been carried out to determine the correct distance and angular relationship between the earpiece and mouthpiece; the design affords maximum comfort to the average person, and the mouthpiece horn has been reduced to make the telephone core hygienic.

The number of spare parts required to be held by an Administration using more than one colour of instrument is greatly reduced.

The colour of a telephone can readily be altered by changing the case only.

CORDS
The telephones are fitted with the latest type instrument cords having PVC insulated conductors and nylon overall braid, ensuring long life and pleasing appearance.

EXTENSION BELL
A magneto extension bell in the G.E.C. Cat. No. BE1100 series (Standard), or BE1200 series (Tropical), can be supplied when specified to provide calling signals at a distant point, or to augment calling signals in very noisy surroundings.

TECHNICAL PERFORMANCE
In comparison with their predecessors, G.E.C. telephones show an improvement in performance of 4-6dB on receiving and 6dB on sending.

As a result of these performance improvements the new G.E.C. telephones will operate over a local line loop of 1120 ohms of 6.5lb cable (5mm conductor) with a performance equal to that of previous telephones operating over a local line loop of 660 ohms, i.e. a local line may be extended by 70%. Alternatively, the new telephones will operate over a length of 4lb cable (.4mm) with a performance equal to that of a previous telephone operating over the same length of 10lb (.6mm) cable.