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:
Auto, c.b., or magneto working
Conversion from c.b. to auto working, and vice versa
Conversion from magneto to auto or c.b. working
Conversion from table to wall mounting and vice versa.
Line performance regulation.
Press button for additional switching or signalling functions.
Tropical finish, with components specially finished and treated to withstand extreme climatic conditions
Amplified handset for users with impaired hearing
Ringer volume control
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
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.
Auto or c.b.
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
the off-hook position
Type N1900 - two-tone version
Line regulation (when required) is provided by a plug-in automatic performance regulator, which limits sensitivity over short lines without affecting performance over long lines. If regulation is not required, the regulator can be inverted in the socket on the telephone base to form an unregulated telephone. When a press button is included for additional switching and signalling functions (e.g. shared service or operator recall) it is positioned immediately in front of the handset cradle and operates a microswitch secured to the main instrument bracket. The button, which is coloured to match the telephone and inscribed with the appropriate legend, may be locking or non-locking according to application.
Type N2208H (Magneto)
Similar to type N2908H convertible
Magneto versions are suitable for connection to exclusive lines or code-ringing party lines. Ringing current is provided by a press button operated transistor generator mounted within the telephone. Power for the generator and the transmission circuit is delivered by a common 6V battery installed near to the telephone. Line regulation is by a fixed attenuation pad, introduced into the circuit by strapping adjustments on the instrument terminal field.
Type N2128H (Magneto)
Similar to type N2188H (convertible)
For use on existing magneto, central-battery-signalling (c.b.s.) or central-battery (c.b.) systems, this instrument is designed to save the expense of replacement when systems are modernised. It is similar to the magneto ETELPHONE and can be supplied with connections appropriate to any of the following conditions and is readily convertible to any other as required.
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.
These are common to all versions of the ETELPHONE:
4.8in x 9.25in x 8.8in (124 x 237 x 225mm)
Telephone (N1900): 3lb 12oz (1 .7kg) net
|Auto table telephone||N1900|
|Auto table telephone with press button||N l 901|
|Auto wall telephone with press button||N1066|
|C.B. table telephone with press button||N1341|
|C. B. wall telephone with press button||N1441|
|Magneto table telephone||N2128H|
|Magneto wall telephone||N2208H|
|Convertible Table Telephone||N2188H|
|Convertible wall telephone||N2908H|
Taken from the Plessey Telephone Catalogue (1971)
Publication No. 7145
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