SWITCHBOARD No's N566 & N569

12 or 25-line
cordless PMBX
indicator signalling


n569.jpg (12310 bytes)These magneto switchboards are suitable for organisations requiring either 12 lines and 5 connecting circuits or 25 lines and 7 connecting circuits.


  1. Positive supervision (Ring off).
  2. Audible alarm.
  3. Lines may be either to magneto extensions or to a magneto exchange.

The 12-line switchboard (shown right) has a sloping panel giving excellent visibility for operation. The French-grey switchboard cover is a one-piece moulding of a durable copolymer plastic. It drops easily into position and is firmly retained by its leading edge beneath the front of the elephant-grey face panel, and by two screws in the rear of the baseplate. Removal of the cover exposes a 3-section chassis which can be opened book-fashion to permit inspection of wiring and components. Each vertical row of keys is removable as a unit. The appearance of the switch- board is enhanced by the elephant- grey handset and by indicators which display a green number against a white background when operated.

n566.jpg (14357 bytes)The 25-line switchboard (shown right) makes full use of lightweight structural materials in conjunction with miniature keys and indicators. The basis of construction is a light but rigid welded steel frame surmounting a hardwood base. The case is formed of replaceable plastic laminated panels, the top and back being a one-piece wrap-over, giving easy access to rear equipment on the release of three captive screws. The key panel, tilted for optimum display of operated keys and indicators, can be swung down to provide full access to internal wiring. Each vertical row of keys is removable as a unit for springset inspection.

The board is attractively coloured; the equipment panel, covered with grained, dove-grey p.v.c. above the black bottom strip and base, tones well with the buff side and rear panels, which are outlined by bronzed metal strips. Black indicators and a black handset and coiled cord complete the overall visual effect.


  1. N9300 type miniature keys with wedge handles having inserts of contrasting colours in the tips so that an operated key is instantly discernible.
  2. Totally enclosed twin-shutter miniature indicators N4832 type are employed; these operate and lock to ringing current and are released by pressing down a projection at the top of the plastic front cover.
  3. Heavy - duty, rotating - magnet hand generator. A transistor ringing unit can be fitted if specially ordered.
  4. Alarm buzzer and cut-off key.
  5. Rocking-armature receiver.
  6. Anti-side-tone induction coil.
  7. The external wires are normally connected direct to the screw terminals in the switchboard but, if a flexible connection is preferred, a moulded terminal block and 72in (182gmm) long black cord can be supplied as an extra.
  8. Full tropical finish.
  9. PVC insulated wires.

Two 3V batteries, one for the operator's telephone circuit and one for the audible alarm circuit, are required. They are supplied only when specially ordered. When a transistor ringing unit is fitted, the audible alarm battery should be 6V.

Equipment Item   Code No.   Height in (mm)   Width in (mm)   Depth in (mm)   Weight lb (kgs)
12-line PMBX   N569   7.75 (196)   21.5 (541)   14 (355)   23 (10.4)
25-line PMBX   N566   12.5 (317)   23 (584)   9.5 (241)   56 (25.4)

Plessey Publication No. 7160 (1971)

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Last revised: October 12, 2019