PLESSEY
GENERAL PURPOSE TELEPHONES
 

The "Etelphone" is a perfectly proportioned instrument moulded in the most modern plastic material combining rich, permanent surface lustre with robust strength. It is designed for highest quality transmission on lines of up to 1,000 ohms loop resistance and is available in black, new ivory, lacquer red, concord blue, topaz yellow, two-tone green and two-tone grey.

Compared with earlier designs it has the following advantages :-

(1) The risk of incorrect dialling is reduced by increased visibility of the dial numbers, which are external to the finger-plate. The numbers are in bold characters on the underside of the transparent plastic ring and cannot be defaced.

(2) The handset is lighter, more comfortable to use, and specially shaped to rest in the hand in the position of maximum efficiency.

(3) No apparatus is attached to the case; it is mounted on the strong composition plastic base-a most convenient arrangement for maintenance.

(4) A single push-button key for Operator Recall, Shared Service, etc., can be easily fitted to a non-button instrument at any time.

(5) Dial connecting wires are included in C.B. sets to simplify conversion to auto.

(6) A key-operated dial lock switch can be fitted to the auto set to prevent unauthorised calls being made.

(7) An automatic regulator unit can be fitted in the telephone to ensure high quality transmission irrespective of line resistance variation.

The telephone has full tropical finish. Connecting wires are insulated with p.v.c. which is moisture-proof and not susceptible to fungoid growth or insect attack. Coils are impregnated, metal parts specially finished and ringer perforations screened.

Two-tone sets have the case in one colour and the handset, number ring, and push key when fitted, in another. The dial dummy of the C.B. set and the key dummy for either set are coloured to match the case.

Instruments normally have a carrying handle under the handset.

Cords are of the p.v.c. insulated type and are normally coloured to match the handset, the desk cord being straight and the handset cord coiled. Similar cords in grebe grey, or nylon braided all straight cords in grebe grey can be supplied.

Taken from the Ericsson Catalogue No. 55

AUTO/CB GP Telephone

The GP telephone is a high-performance instrument of advanced design and wide application. Available in four types, it is suitable for use on central-battery or automatic telephone systems and for table or wall mounting. When required, inter-type conversion can be readily accomplished by means of appropriate component kits supplied on demand.

Main Features
Easy conversion
Modular shock-resistant construction
Printed-wiring board with miniature components
Stain-resistant, high-impact shell mouldings
Carrying handle
Easily visible dial characters
Automatic line regulator
Ringer-volume control
Optional press button for operator- recall, shared-service or bell on/off operation
Optional amplified handset
Wide colour range
Standard or tropical finish

Cover
The cover consists of a one-piece ABS copolymer moulding of high gloss finish and high-impact strength. A carrying handle is fitted across the handset cradle.

An aperture, provided above the dial to accommodate a press-button, is closed by a dummy button when not required.

Dial
The dial is the conventional trigger type. A clear-plastic fingerplate and a number ring with an antique-silver background make the black characters easily visible even in poor light. Dial markings can be provided to any specification (Arabic, Chinese, etc.). The clear-plastic number card protector can be removed with a simple rubber suction disc. In the CB version a dummy dial is fitted.

Handset
The lightweight handset is a one-piece moulding in ABS plastic with screw-on mouthpiece and earpiece. The inserts are the replaceable capsule type. An amplified handset can be provided as a direct replacement for the standard handset. It is suitable for use by persons with impaired hearing or in locations where reception is difficult.

Terminal Block
The 6-way terminal block consists of a base and cover moulded in polystyrene, the cover being fixed by a single captive screw.

Cords
The conductors of the cords are copper-tinsel with p.v.c. insulation and spade-type terminations. The outer sheath is of flexible p.v.c. Grommets, fitted to both ends of the cords, lock into entry holes of the terminal block and main instrument to act as strainers. The 4-way coiled extensible handset cord, 216 mm (8.25in.) long when coiled, extends to 1780 mm (6 ft). The non-extensible 3-way line cord has a standard length of 6 ft; various non-standard lengths can be supplied.

Baseplate
The polystyrene baseplate accommodates the cradle switch bracket, ringer and gongs, dial assembly and printed-wiring board. Four domed chloroprene rubber feet prevent the instrument from sliding even on highly polished surfaces. Two slotted domes, protected by a mesh in the tropical version, provide for ventilation and a good sound outlet.

Printed-Wiring Board
All speech-circuit components except the transducers are mounted on the printed-wiring board, to which all incoming and outgoing connections are made. The automatic line regulator components are connected so as to form a variable loss network, maintaining speech levels constant irrespective of line length. The cradle microswitch has a low operating pressure and requires no maintenance; its reliability is greatly improved compared with earlier types of switch.

Ringer
The unicoil ringer combines simplicity of construction with a good sound output. A knurled wheel projecting through the baseplate provides the means by which the output volume can be adjusted.

Maintenance
The cover is easily removed, being secured by two screws fixing the handle. The outer dial ring, close-fitting to the dial and a floating fit on the cover, facilitates cover removal. A manually operated latch locks the cradle switch in the handset-on position, allowing calls to be received with the cover removed for instrument inspection. Ringer, bell gongs and printed-wiring board are readily accessible and easily replaced.

All cord conductors have spade terminations, allowing easy connection to the screw terminals of the instrument wiring board, terminal block and handset inserts. Dial assembly contacts are protected from dust by a clamped-on plastic cover. Trouble-free operation over long periods is ensured by robust construction and reliable components.

Colour Range
All models are available in black, ivory, blue, yellow, red, two-tone grey, and two-tone green. In two-tone colours the handset, terminal block, outer dial ring and cords are in the darker tone.

Specification

Dimensions and Weight
Base: 215 x 146 mm (8.5 x 5.75in.)
Height: 124 mm (4.8 in.)
Length of handset: 238mm (9.2in.)
Weight, telephone: 1280g Weight, handset: 220g

Cover and Handset
ABS high-impact plastic

Baseplate and Terminal Block
High-impact polystyrene

Cords
PVC insulated copper-tinsel conductors in flexible p.v.c. outer sheath. Spade terminals. Handset cord: 216 mm (8.5in.) coiled, 1780 mm (6 ft) extended. Line cord: 1780 mm (6 ft) standard, with other lengths available.

Cradle switch
Microswitch, B PO type 20A.

Dial
BPO type 21 FA trigger dial.

Dial Characters
Black on antique-silver to any specification (Arabic, Chinese,etc.)

Dial Speed and Ratio
10 p.p.s. and 2:1 standard. Other ratios can be supplied.

Handset Transducers
Receiver: rocking armature replaceable capsule, BPO type 4T
Transmitter: carbon granule replaceable capsule, BPO type 16

Amplified Handset
20 dB maximum gain

Regulator
Transmission and reception zero line sensitivity attenuated by 5 dB. Attenuation decreases with line length to 0 dB at 400 C2.

Ringer Type
Unicoil, BPO type 79A. DC resistance:
1000 ohms Impedance at 25 Hz: 3 k ohms Impedance at l kHz: 10k ohms Ringing current: 15 to 30 Hz.

Bell
Double gong: harmonising tones.

Colour Range
Black, ivory, blue, yellow, red, two-tone grey, two-tone green.

Taken from the Plessey Telephone Catalogue (1971)

Last revised: December 10, 2019