GPO Telephones - Type 150

Type 150

The 100 series, 'candlestick' two-piece telephone is much sought after these days. This one is a Tele. 150L circa 1929. The L denotes the addition of the original slipping cam Rotary dial, as distinct from the CB (central battery) version, which was without any dial and relied entirely upon connection via the operator. As shown this Tele. 150 has been brightened up by the removal of some of the plastic coating which originally covered all of the brass construction. At this time brass was considered a very cheap and utilitarian material, so was usually covered up. The transmitter (microphone) was of a very poor, carbon granule construction, which absorbed moisture and required regular replacement. The low cost, however, ensured that this transmitter would continue to be used for many years to come. In contrast, the twin coil and diaphragm receiver was of very good quality, indeed. The Tele. 150, like its successor the Tele. 162/232, was actually only the 'front end' of the telephone. Containing only the transmitter, receiver and switch hook assembly; the entire electrical telephone circuitry was contained within an accompanying magneto bell set. This was initially the wooden cased version shown or the later, compact, plastic, Bell set 26. Though it is a common misconception, the GPO never did use Bakelite in the construction of any of its telephones or associated equipments, such as the Bell set 26, as it was far too brittle. The black material usually confused with Bakelite was always the far more robust material, Urea Formaldehyde Resin.