Although some telephones were moulded with other plastics all of the ones on show here are made in ABS (Acrylonitrile butadiene styrene) - see Wikipedia for information. Like Bakelite it moulds cleanly and has a glossy finish. Although still brittle, it is much more flexible than Bakelite, is cheaper to mould, not needing high pressures, can be readily coloured, drilled or machined. However, it is a thermoplastic. Engineer, keep your soldering iron away from the case!
Telephone 706 replaced the 332 as the Post Office's standard instrument from 1959. Later
models were fitted with the carrying handle across the cradle rest. The first BPO phone
to have a regulator to adjust the receive volume on short lines. A range of colours
was readily available: black, ivory, two-tone green and grey, red and mustard. This
one has been fitted with a later dial with a clear finger plate. The original would
have been green to match the body.
The same circuitry as the 706 but in a cost reduced version with a restyled case. The handset
can be parked in the off hook position as shown on the right. The same range of colours
was available as for the 706. The black colour was not very
popular with domestic subscribers and found itself mostly in business use. Ivory and
two-tone grey were most popular for home use. At the very end of production after
telephone instruments were liberalised a range of
exotic colours, such as tangerine, were made available.
Commonly used in offices and small business. An installation consisted of the Planphone
plus one or two extensions. Exchange calls can be answered on the Planphone and switched
through to either extension. A intercom feature allowed a private conversation between
the Planphone and one or other extension. Details of the buttons on the Right. The Planphone
was made up of the Planset N625 as the base with a telephone 706 with modified wiring mounted
on top. A local 10 Volt power supply was also needed to complete an installation.
This is basically a telephone 746 modified for Dual Tone Mutli-Frequency (DTMF)
working. The keypad and tone circuitry mounted on a special bracket which fits the
holes normally used to fix the dial. Made in 1974 and supplied for PABX use,
since the public network at that time did not support DTMF. This probably explains
why it has an SA (subscribers? apparatus) number rather than one in the 700
series.
Not actually plastic, since the case is pressed steel, but from the same era is the Loudspeaking Telephone No 4. By no means the first loudspeaking telephone from the Post Office, but probably
the first to use voice switching to avoid feedback (howling). Its metal case
makes it rather heavy. Intended for executive desks, and when privacy was needed a
handset mounted at the rear could be picked up which cut out the loudspeaking
feature.
The trimphone was a radical departure in style for the Post Office, with its fore and aft handset placing and neat styling. The first standard British telephone to use a tone sounder, with volume adjustable by a wheel on the right from quiet to loud or crescendo. The works
were hardly miniaturised at all and appear to be a real shoe-horn of a job to get in the case.
The dial model was so light it tended to skid around while the dial was being wound up. The later push-button version (right) did not suffer from this problem.
Another novel feature was the microphone, which was mounted just below the receiver and fed by a sort of speaking tube arrangement from the mouthpiece at the base of the handset. When the telephone is off-hook, the cradle rest forms a convenient carrying handle for the telephone.
A late BT model from 1982. The compact phone, Telephone No 776, is rather similar to the Jubilee Model, produced in 1977. This one was acquired at a THG swapmeet.
Only the transmission elements are contained within the case; there is no internal sounder. A separate bell set was used, which formed a shelf to stand the phone on. Unfortunately the one on the left didn't have the matching bell set. I have subsequently acquired a complete, but dirtier, model, as on the right. The cords come out of the sides towards the back - handset on the left and line cord on the right. The line cord is quite long and coiled allowing the user to walk around with the telephone.
Next some telephones from private telephone systems
Bakelite
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