| Desk Telephone 1746
Catalogue No. T101
 The
desk telephone Type 1746 is manufactured to meet the stringent requirements
of the British Post Office 700 series of telephone instruments.
Finished in non-scratch ABS plastics, the '1746' is supplied in a wide range
of non-fading colours including two-tone combinations. Provision is
made for fitting up to two keys and two lamps, to give facilities for shared
service, exchange recall, priority, and main/extension calling when used in
parallel.
The design incorporates printed wiring boards and the use of modern
miniature components which provide utmost mechanical and electronic
reliability. Ease of servicing is ensured by the simple internal
layout.
Dial pulse ratio of 2:1 or 1.6:1 is available.
Fully tropicalised versions are available, where all components are
finished to better than BS.2011 Category 10/055/21 and the telephone meets
the specification of Preece Cardew and Rider.
Alternative types
Apart from the normal direct line automatic instrument, versions with dial
removed and a dummy dial substituted can be supplied for operation on
central battery systems.
Other versions to supply the following facilities are available or can be
produced from the basic instruments by use of conversion parts:-
- Shared service line - automatic systems.
- 2-wire PBX extensions with recall.
- PMBX extensions with additional 'C' wire signalling.
- PMBX operators' telephones.
- Hotel telephones with 'message waiting' lamps and/or guest service
symbols. (Cat. No. T105.) Press button and magneto versions are also
available. (Cat. No. T150 and Cat. No. T103/4.)
Colours
Black, two-tone grey, ivory, two-tone green, blue, red. (In dual-coloured
telephones the handsets and cords are in the darker tone.)
Accessories
- Bell cut-off key Cat. No. A441.
- Press-to-talk handset Catalogue No. A434.
- Wall conversion kits Catalogue No. A481.
- Handset retaining clip for use in maritime conditions and extra long
line cords to special order.
Exterior
Case and handset moulded in ABS copolymer of acrylonitrile butadiene and
styrene.
Cords
PVC-covered cadmium-tinsel conductor cords. Held in position by grommets
which relieve conductors of any stresses. Line Cord, straight: 3000mm.
Handset cord, coiled: 250mm, uncoiled 1700 mm.
Cradle Switch
Sealed microswitch.
Dial
Articulated-trigger type with self-compensating action. Projects through
self-centering ring on case. Characters printed black on silver
background beneath clear plastics finger plate.
Speed: 10pps nominal.
Interdigit pause: 240m5 minimum Break-to-make ratio: 2 : 1 or 1.6 : 1.
Other ratios are available.
OVERALL TRANSMISSION CHARACTERISTICS
Transmitter
Carbon granule replaceable capsule type. The change in sensitivity
over the input range 3-30 dynes per sq. cm. is less than 5db at a given
frequency in the range 300-3400Hz.
Receiver
Rocking armature, replaceable capsule type.
Automatic Regulator
An automatic regulator is fitted to limit speech-signal amplitudes on lines
shorter than 400 ohms: introduces virtually no attenuation on longer lines.
Ringer
Double coil, D.C. resistance 1000 ohms, impedance 2000 Ohms at 25Hz, 20Kg at
1000Hz. Accepts ringing currents of between 16 and 30Hz. Bells, double
gong, harmonizing tones. An extension bell can be connected if
required.
Dimensions/ Weight (unpacked)
Height - over handset 127mm
Width - over handset 237mm
Depth - 216mm
Weight - 1.5kg
Taken from Publicity Leaflet 2.5/A.A/3.78 (dated 1978)
Desk Telephone 1746PB (Push Button)
This push button telephone may be connected to any
step-by-step office simply by transferring the wires from the existing dial
telephone. Use of the latest micro-electronic techniques including
4-phase MOST made possible the size, price, performance and reliability
hitherto unobtainable. Ample storage is provided (16 digits), for
international dialing codes and DDD service.
Dial pulse speeds of 10, 16 or 20 PPS are available
by a strapping option. A unique collapse action of the push buttons
reduces error rates.
The telephone is suitable for use on line loops
with a resistance up to 1000 ohms.
Ringing current range 15 to 30 Hz.
Handset and case are moulded in a high grade ABS
plastic. Standard colour is 2-tone fawn (grey). Full colour range
available with minimum quantity orders.
Unit is line powered with a self-contained nickel
cadmium battery charged via telephone wire.
Can be operated in parallel with an ordinary dial
set.
Taken from TMC Product profile (Canada)
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