PYE/TMC TELEPHONE No's T120 (Type 704) and T121 (1705)

Linesman's Telephones
Standard version 704 and Field version 1705

Catalogue Nos. T120 (Type 704) T121 (Type 1705)

Pye TMC Linesman's telephones are rugged, all-weather, portable instruments. The instruments are completely self-contained and are equipped with a dial and integral transistorised ringing generator powered by internal batteries.

Type 704 is used by line maintenance engineers above and below ground. Pye TMC is a major supplier of this type of instrument to Post and Telecommunications Authorities throughout the world and is the principal manufacturer in the United Kingdom.

Type 1705, which incorporates a high-powered ringer, is designed for use by Armed Forces, civil engineering, railway, harbour and shipping authorities, and for general field requirements.

The case is of extremely robust high impact resistant plastics to give good service even under the most adverse conditions. The carrying handle is of nylon webbing with chromium plated fittings.

The deck panel is fitted by two captive screws and a weatherproof seal is formed by a neoprene gasket. The handset, gravity switch, plungers, dial, 3-position slider key, line terminals, headset jack, and two tone injection sockets are all carried on the top of the deck panel.

The local battery container is a fully insulated drum, the outer end of which is provided with a moulded screw cap which is a flush fit with the outer surface of the case.

Technical Data

Transmission standards
The sending /receiving efficiency and level of sidetone are the same as the latest BPO telephone 746 and the instrument is fitted with an automatic line regulator. It is designed to be used on C.B. manual or automatic exchange lines up to 1000 T.E.R. (Transmission Equivalent Resistance) and on longer lines when used as a local battery telephone.

Telephone handset
A standard telephone handset is provided containing a No. 16 carbon granule transmitter and a No. 4T rocking armature receiver. A small switch is also provided for opening and closing the transmitter circuit.

The latest BPO type trigger dial is fitted marked with figures. Where a dial is not required a dummy dial is fitted.

Ringing generator
Type 704. Silicon transistors provide a ringing current sufficient to ring 4 x 1000 ohma bells and one 1 .8uF condenser all in series, or 2 x 1000 ohms and capacitors in parallel.

Type 1705. The ringing generator incorporated in this version has a higher output. With the battery at 4 volts the generator is capable of energising the buzzers of two similar instruments in parallel at the end of a 4000 ohm line.

4.5V local battery
Three 1.5 volt U2 (or equivalent) dry cells are accommodated as described previously and power the ringing generator and energise the transmitter to provide a standard local battery transmission circuit. The local battery is also arranged to supply transmitter current to a distant CB/ Auto telephone if the line is disconnected from the exchange power.

3-position key
Is fitted with a sliding knob to provide the circuit conditions for either CB/Auto or local battery working and connects ringing current to line when held in the non-locking position.

Other features
AC buzzer for indication of incoming calls.
Two 4mm sockets for use with amplified probe detector.
A jack with protective cover is provided for connection of headset.
Two line terminals. These are screw terminals provided with 4mm sockets in their tops.

A light weight headset fitted with a suitable plug can be used in circumstances of higher ambient noise. (Cat. No. A437).

Special carry case
Whilst the plastics case of these instruments provides good protection, a separate carrying case is available as an optional extra. This heavy-duty case is made from polyurethane impregnated nylon and has a nylon webbing carrying-strap (Cat. No. A424).

Height - 150mm
Width - 330mm
Depth - 165mm

Weight with batteries:
Type 704 - 2.52kg
Type 1705 - 3kg

Taken from Publicity Leaflet AA/1.78/2.5M (dated 1978)

Operating instructions


Wiring diagram


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Last revised: February 18, 2022