BT CADET 1 + 6

PXML No. 84

The Cadet is a microprocessor controlled call connect system with a capacity of 1 exchange line and up to 6 extensions.

The central control unit (CCU) is wall-mounted and houses:-

  • The principal circuit board carrying the control circuitry exchange line connection and 3 extensions.
  • The expansion board providing 3 further extensions.
  • The mains fail reset board.
  • The power regulator assembly and mains transformer.

The system uses standard 2 wire 10 pulse per second (pps) telephones. A dedicated Cadet System-phone is also available.

Dimensions CCU measures approximately 300 x 200 mm x 75 mm and weighs approximately 2.7 kg.

Made by GEC Telephone Division in the UK.

Approved for direct and for indirect connection (LD signalling) to the PSTN by working as a (List b) subsidiary system connected to a (List c) PBX.

The system supports earth loop recall signals only.
Approved software is: Level H. As shown on the label on the microprocessor IC4.

240 Volt, 13 Amp, 50 Hertz Mains Supply.  Power consumption typically less than 20 watts.


Cadet 1 plus 6 CCU 870239
Fuse 72/0.25 314215
Line Jack Unit 2/1A 373901
Cadet 1 plus 6 Systemphone 870263

Idle - Normal capacitance loop with Gas Discharge Tube protection.
Seized - Normal Telephone loop.
Held - Approximately 300 ohm loop.
Mains fail - Normal telephone condition.

Terminals must employ LD signalling.
A recall switch is not required unless system is subsidiary to a host PABX.
Ensure correct polarity of line to host PABX.
Incorrect polarity will result in the line being released when the recall switch is operated.

The flowing phones are known not to work with the Cadet:-
Facilityphone 300
Kirk and Kirk 30
Statesman 9001 & 9003
Viscount Super 12

Line Jack Unit connections

Cadet System phone socket

Extension terminal block Cable LJU -/1A
A White/Blue 5
B Blue/White 2
C Green/White 1
D White/Green 6

Standard telephone socket

Extension terminal block Cable LJU -/1A
A White/Blue 5
B Blue/White 2
Earth strip White/Orange 4

See also Minimaster 1


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Last revised: November 23, 2021