These switchboards are made for any multiple of 10 lines up to 160 lines in the answering field with the exception of OB 5500 which is made for up to 200 lines. All types are made for any number of cord circuits up to 19. The capacity of the multiple with four panel multiplication is 800 lines, except for OB 5500 where it is 1600 lines. The types OB 5400 - OB 5600 have mechanical restoring devices for the clearing signals. The various types have the calling devices indicated below.

OB 5300: drop indicators.
OB 5400: combined jacks and drop indicators.
OB 5500: indicator jacks.
OB 5600: visual indicators.

Type OB 5400/100/12 is pictured.

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

In 1939 the OB 5300, OB 5400 and OB 5600 were renumbered as the ABK 60, ABK 62 and ABK 64. See below for further details.

The cords are made in two colours: red and grey.  Odd cord circuits have red cords and even cord circuits have grey cords.

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)

ABK 60, ABK 62 and ABK 64
These switchboards could be supplied with 80 lines (10cords), 100 lines (12 cords), 120 lines (13 cords) and 160 lines (16 cords).

Dimensions:
Height: 1600mm, width: 632mm and depth 830mm.

ABK 60 (Replaced the OB 5300)
Drop indicators.

The ABK 60/100/12 is shown pictured.
 

ABK 62 (Replaced the OB 5400)
Combined jacks and drop indicators.

The ABK 62/100/12 is shown pictured.
 

ABK 64 (Replaced the OB 5600)
Visual indicators.

The ABK 64/100/12 is shown pictured.
 

Last revised: November 24, 2025