The General Post Office (GPO) of the United Kingdom carried the sole responsibility for providing telecommunication services across the country with the exception of Hull. The GPO issued a range of telephone instruments to telephone service subscribers that were matched in function and performance to its telephone exchanges.
General history
Until October 1969, the GPO had a monopoly on the provision of all telephone lines and telephones within the UK, other than in Kingston upon Hull, which for historical reasons was unique in maintaining its own municipal telephone service. From 1 October 1969, the Post Office Corporation replaced the General Post Office with ownership of the former GPO business. Customers of the PO (known internally as "subs", short for 'subscribers') did not own their telephones. They were instead rented from the GPO, together with the house wiring and the wiring connecting the house to the local network at a connection point known as a DP (distribution point), which was generally located at the top of a nearby telegraph pole.
During the early days of telephones, in the UK, a variety of instruments were produced, in low volume, often combining new and emerging technologies with the traditional skills of the wood joiner and cabinetmaker. They were simply known as Type 1, 2, 3 etc. These were often used on simple, internal links, sometimes taking the place of the 'speaking tube' in large houses. These instruments had no dials, and signalling consisted of a hand-cranked magneto generator. Often the bell at the other end would just be 'tinkled' by simply rattling the switch hooks up and down.←From these developed the first, serious, GPO instruments, the 100 series. This comprised the Type 121, a wall phone, and the Type 150, a desk phone.
Types 121 and 150
Both were based around the same handmade, wooden case, containing the telephone circuit and bell. The Type 121 had the transmitter mouthpiece screwed onto the front of the box and the switch hook, holding the receiver, protruding from the left hand side. Below the mouthpiece was a dial-mount, which either contained a dial (F or L - Figures only or with Letters - from about 1926) or a blanking plate (CB). This made it a true, one-piece telephone which was available either 'stand alone', mounted on a handsome, wooden, back-board, with integral writing desk or, as a Tele. 123, combined with the original, Button A & B coin-box.
The Type 150 'candlestick' two-piece telephone is now a collectible item. The bell receiver was originally coated in a black vulcanised rubber (Vulcanite) and the remaining brass work had a black oxide finish (In the photo the original black finish has been stripped to reveal the brass; the dial is also later, the original number 10 dial would also have been finished in black oxide on copper.) The L denotes an alphanumeric (rather than number only) dial plate. The dial uses a slipping cam Rotary dial - distinct from the CB (central battery) version - which was without any dial and relied entirely upon connection via the operator. The transmitter (microphone) was of a very poor, carbon granule construction, which absorbed moisture and required regular replacement. However, the low cost 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 Type 150, like its successor the Type 162, 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, Bakelite, Bell set 25.
Type 162 & 232
The 162 was originally launched in 1929 as the last of the 100 series. Once its potential was realised it was quickly promoted to a Type number of its own, becoming in 1934 (with some internal modifications) the 232 and staying in production until 1957.
The Tele. 162 Handset Micro Telephone, was the first UK phone to incorporate the transmitter and receiver into a single unit, 'The Handset', which had not been used on telephones in the UK since the very early metal and wood cased models, and the BPO preference for a separate transmitter and Bell receiver, as on the Tele. 150 and Tele. 121.
It was designed as a very lightweight domestic phone, which could be carried around whilst in use, by hooking the fingers under the switch-hook cradle. For this purpose it could be ordered with an extra long instrument cord at additional cost. It was even with a blanking plate instead of the dial. Like the Tele. 150, it required a Bellset 25 to complete its electrical circuitry and to provide bells. This could be either screwed directly under the telephone or mounted separately in another location.
The Tele. 232 came out of the box fitted with a base plate containing a drawer, holding a personal directory card. The telephone could then be screwed directly onto the matching Bell set 26, making a true, but very heavy, telephone set, or screwed down onto the desk of a CCB (coin collecting box), in a Public Telephone Kiosk. In this form it was fitted with a modified dial, a more durable handset cord, and was re-numbered as the Tele. 242. There was one other variant. With modified internals and designed purely to be used in combination with a Bellset 39a or 44, this was the Tele. 248 in the guise of the Extension Plans 5 & 7. This type of telephone is often featured in British made period television dramas. Curiously, the telephone often rings despite not being fitted with any bell unit.
Plan 5 and Plan 7 This was the GPO's first attempt at a compact, supervised extension plan, for small businesses. The Plan 5 had 2 extensions plus the control station, the Plan 7 had only 1.These instruments were manufactured for the BPO by GEC.
The main operator control units, of these plans, appeared similar to a 232 plus Bellset 26 combo but was now a Tele. 248 plus Bellset 39a (early versions) or 44 (later). These Bellsets 39a and 44 were Bellsets in name only, as they contained no bell. What they did contain was a maze of spring contact sets, mainly activated by a cam at the pivot of the slide switch, which was a horizontal, quadrant mounted, 4 position slider, positioned via a recess in the front of the Bellset case, and was flanked by either 1 or 2 press buttons, for buzzing the extension(s). The main instrument required a separate, remote mounted bell, for signalling of incoming exchange calls.
The main instrument could make and answer exchange calls, talk to and transfer calls to the extension(s). The extensions could call and talk to each other and the main instrument, but could only make external calls if a request to the "operator" at the main instrument, for the exchange line to be switched to the extension was honoured.
Power for intercommunication signalling and speech circuits between the main instrument and the extension, when not on an exchange call, was provided by dry cell batteries at the main instrument.
The early extension instruments were also 200 Type telephones, mounted on a Bellset 39a or 44; but these were modified to remove the switching mechanism and contained an integral bell for exchange line signalling when the exchange was switched through to the extension and a buzzer for intercommunication signalling from the main.
Later extension instruments were: for extension 1 the Tele. 321 or 328 and for extension 2 the Tele. 326 or 327.
When this system was eventually revisited and brought up to date, with the 700 series Plans 105 and 107, the equivalent control unit was dubbed 'The Planset'.
Type 332
The 300 series equipment was introduced in 1937. The Tele. 332 ASTIC, Handset Micro Telephone was the standard telephone instrument issued by the GPO from 1937 until 1959, although 242Ls continued to be supplied for pay-on-answer kiosks. Essentially it was a redesign of the 232/bellset 26 combo. The term ASTIC indicates the use of an anti-sidetone induction coil, to permit only a small, controlled amount of speech signal back to the talker's ear to provide necessary sidetone for a natural communication experience. It continued in production until the mid-1960s. This was usually only available in black although ivory, red and, the especially rare, green were also produced. Although 332 is the generic for this model, by dint of superior numbers, there were four other models in the range. The glossy, sharp styled 332 gestated from the much poorer quality 330. Though similar, the quality and finish of the 330s moulding was poor, by comparison. Then there were the button phones. A 332 with the facility for one button is a 312, two buttons a 328 and three buttons a 314. For this reason, in the photos below the instrument on the left is, strictly speaking, a 314 and the one on the right a 312, despite the fact that their full potential is not being utilised. The Tele. 332L shown on the left is a bedside extension from an Extension Plan 1A. BELL ON BELL OFF push buttons were added, forward of the switchook cradle. The centre button position is filled with a blanking stud and only a 2 way label is installed. The instrument on the right is a Tele. 312, but has its single button hole fitted with a blanking stud. The label screws are sitting redundant in their holes.
House Exchange System The 300 series was much more than just the Tele. 332. There was a whole range of similarly designed products. Fieldsets (Tappers), Headsets, Pendant Telephones, Wall Phones and the House Exchange System. Many private telephone companies had sprung up in the UK. As these were banned by law from connecting to external lines, they contented themselves with producing systems for automatically dialling between company offices, within the same building or, via private wires, rented from the GPO, virtually anywhere. The GPO could only do this via PMBXs (manual switchboards), ranging from the two to five line cordless boards, via the 25 and 50 line plug and cord boards to the mighty PMBX 1A, which, with its modular construction, could be any size a large company might require. The GPO regarded the private telephone companies as a thorn in their flesh and a great loss of potential income. They decided to tap into this lucrative market. Initially, they produced a system virtually identical to the competition and called it the House Telephone System. This appeared, from the rear, like a Tele. 332 but the front sloped down and was covered in two rows of buttons, by which a few other, similar, extensions could be called. Like the competition, this system was entirely internal and could not connect to the PSTN (Public Service Telephone Network). Unlike the competition, however, the number of extensions which could be incorporated was strictly limited. The GPO tried again.
The 300 series House Exchange System, now known as the HES1, was a combination of the Tele. 332L and the House Telephone System. From both the front and rear elevations the instrument appeared as a normal 332L. From the side, however, it was a different story. The snout of the instrument had been stretched forwards a full 8 inches in order to mount two rows of call buttons along with their plastic covered labels forward of the switchooks. All stations could make and take external calls, call any other station and also transfer calls between them. For the first time, small companies did not need to employ a telephonist – a big selling point. The main downside was that the central branch exchange unit was mains powered and used 50 Hz AC relays to route the calls. It had to be found a place out of the way as it was extremely noisy, the noise level increasing as calls were connected and relays energised.
Bell Sets 25, 26, 31, 56, 59