The switch is designed for operation with a magneto telephone instrument and has press buttons as switching devices.

The switch is made for 3 lines only.

This wall type switch supersedes the OA 150.

This wall switchboard has fixed mounting and cannot be extended.

The switchboards are fitted in cases of dark stained, polished oak.

The microtelephones are our modern Bakelite type. The generators have 5 magnets. All conductive parts are fitted on insulating material of high quality.

Electric properties.
All switchboards are made for doubles line working but may, of course, also be used for single line working. The induction coils are anti-sidetone connected. The microphone supply has been arranged so that microtelephones without key are used.

The parts belonging to 10 lines, consisting of 10 calling signals and 10 jacks with terminal strip are joined to a separate lines group set.

The necessary parts for one speaking circuit, consisting of one cord circuit with accessories, key, clearing indicator, and terminal base, are joined to a separate switching set.

The parts are simple to fit in the switchboards, which makes extensions very simply to carry out. This, however, does not refer to the smaller types of wall switches which cannot be extended.

All switchboards are fitted with terminals for the lines and consequently the lines are in no case connected direct to the jacks.

Batteries are supplied only on special request. They can be made up of dry cells or storage batteries. The tension of the microphone battery should be 4.5 Volts for all switchboards. The tension of the signalling battery for wall switches and switchboards with drop indicators, combined drop indicators and jacks or indicator jacks should be 4.5 Volts, and for switchboards with visual indicators and all multiple switchboards it should be 6 Volts.

Taken from the L. M. Ericsson Catalogue No. 188 (1934)

Last revised: March 29, 2024