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1000 type to Plug and Socket and circuit diagrams
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GEC 1000 TELEPHONE
The new range of G.E.C. subscribers' telephones offers Administrations a very high level
of performance from instruments that are available in a variety of shapes and colours.
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
"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.
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.
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.
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
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.
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.
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.
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.
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
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
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
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.
The telephones are fitted with the latest type instrument cords having PVC insulated
conductors and nylon overall braid, ensuring long life and pleasing appearance.
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.
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.
|"G.E.C. 1000" Telephone, automatic
|"G.E.C. 1000" Telephone, C.B.
Taken from the GEC catalogue leaflet STL13 (Dated around 1957)
See also Tel/9T and TEL/10T
|Side view showing one of the ventilators,
which also served as finger lifting grips
|Close up of dial
|TEL/2T/AAT - General view
|TEL/2T/AAT - View of chassis
|TEL/2T/AAT - Components and terminal block
|TEL/2T/AAT - Close up of vent/finger grip
|TEL/2T/AAT - Base plate