GPO Telephones - Type 706

Type 706

The 700 series was the GPO's response to public demand, fuelled by American television shows, for a modern design with a helical, anti-tangle handset cord. The Telephone No. 706 was a revelation when it was first released in 1959. Again, still also available in CB (no dial) form, it was a robust design which is still in use today in the UK, suitably modified for use with the New Plan BT sockets. It was available in two-tone green, two-tone grey, topaz yellow, concorde blue, lacquer red, black and ivory.

The 706 was manufactured to a GPO design, by several manufacturers. There were two basic designs: one with a modern printed circuit and another with a wiring loom. Other variations included: metal or plastic baseplates and the presence or absence of a metal carrying handle.

The very first 706s had a metal dial similar to the 200 and 300 series phones. Later phones had a plastic dial. In both versions letters and numbers surrounded the dial. 706s are usually marked 706L, which indicates that they have a lettered dial. The 706F with a figure only dial, the same as on the 746, and a plain ring around the dial with no letters or numbers was introduced in 1969.

• 706 Two Tone Green Telephone manufactured 1963. This sample unfortunately has a cracked dial, but is an early version as later dials were clear

• 706 Telephone inside showing the reversible regulator mounted vertically and shown in circuit

A feature of the 706 was a regulator that could be used or not. The idea was, that if the subscriber was close to the exchange, the regulator would reduce the sensitivity, as it had been found that this telephone was too sensitive close to the exchange and also had a propensity for picking up radio broadcasts, from strong stations, mainly taxis. The purpose of the regulator was to vary the amount of ac speech current flowing through the transmitter and receiver, to prevent it being considered too loud by subscribers on short lines. The regulator consisted of a network of rectifiers, diodes, resistors and two thermistors.

The regulator could be removed from circuit, for customers not close to the exchange. This was achieved by turning it upside down, which substituted a shorting link instead of the components. In practice the unit was normally left in circuit. Compare this with the inside of a 746 where the regulator is permanently built in.

• 706 Regulator unit, the red part being a string of diodes and the glass part are the thermistors. Note the thermistor is painted black to stop the glow being shown

• 706 Regulator reverse]

The 706 style telephone was also produced for non GPO subscribers by many of the same manufacturers that produced telephones for the GPO. These telephones can be identified by having no "706" reference on the underside and will usually have the manufacturer's own reference instead. Whilst most of these phones were superficially similar to the GPO 706 many had different internal parts including "tropicalised" versions for counties with high humidity or potential insect ingress.

• TMA7214 built by The Telephone Manufacturing Co in 1979 using electronic parts similar to the contemporary 746.

• Ericsson Etelphone with optional wall mounting kit

• GEC New Gecophone

NB: There were a number of hybrid types between the 300 and 700 series. These appeared as 332s but fitted with a 700 series handset and cord. The most interesting of these were the 'Intinsically Safe Telephones'. These had 323 style bodies of a sealed metal construction in a grey hammer finish. These were for installation in environments where there was a risk of fire or explosion from sparks, such as mines and chemical plants.

The 700 series was much more than just a single instrument. There were the Teles. 710, 746, the 711/741 wall phones, pendant telephones, headsets, re-styled bellsets, connection blocks and distribution panels. A full, matching range. Then there was the HES3.