|Auto, CB, Magneto, and Convertible ETELPHONES
The ETELPHONE range combines high performance with attractive appearance and wide
application. It includes the basic instrument (Type N1900) designed in conjunction with
the British Post Office and caters for the following requirements:
All versions are similar in external design and available in pleasing light-fast colours: black, ivory, concord blue, topaz yellow, lacquer red, two-tone green and two-tone grey for auto and c.b. instruments and black, ivory, and two-tone grey for magneto instruments.
The instrument case and handset mouldings are of ABS copolymer, a high-impact material impervious to cosmetics, inks, oils and most chemicals. Table telephones are complete with a moulded desk connecting block in matching colour, and both table and wall instruments feature a convenient off-hook position for the handset.
The transmission circuit ensures maximum frequency response and line sensitivity over exchange lines with loop resistances up to 1000 ohms and includes (a) an induction coil with high anti-side-tone properties; (b) transducers of sealed capsule type to facilitate maintenance, and (c) contact springs tipped with precious-metal contacts to ensure maximum contact reliability.
The instrument ringer is designed for long life and freedom from adjustment after manufacture. It is of the single-coil type and employs a high-retentivity ceramic magnet with torsion reed suspension. Instrument wiring is point-to-point with soldered connections. Conductors are insulated with p.v.c., a material fully resistant to moisture, attack by insects and fungoid growth. Desk and handset connecting cords are additionally protected by p.v.c. sleeving. External conductors terminate on screw terminals on the instrument terminal field.
These types are suitable for use as main or extension instruments. The automatic instrument is equipped with a BPO Type 21 dial, adjusted to transmit 10 p/s with 2:1 break/ make pulse ratio. The dial number ring is fitted externally and bears standard numbering, i.e. 1 to 0. Alternatively, dials can be supplied with adjustments and numbering to suit customer requirements.
Type N1065 with handset in
Type N1900 - two-tone version
Type N2208H (Magneto)
Type N1341 (central battery) with press button
Stock instruments are in tropical finish, and include a transistor generator, wiring for both a dial and a plug-in regulator, a 5000 ohm ringer and capacitors within the ringer and receiver circuits. A diagram is supplied with each instrument, indicating the various strapping adjustments and equipment requirements (where necessary) for conversions 1 to 10 above. Conversions do not affect the induction coil.
Taken from the Plessey Telephone Catalogue (1971)
Last revised: October 01, 2019