These switchboards are made for any multiple of 10 lines up to 160 lines, with the exception of OB 4501 and OB 4502 which are made for up to 200 lines. All switchboards are made for any number of cord circuits up to 19. The types OB 4401 and OB 4602 have mechanical restoring devices for the clearing signals. The various types have the calling devices and lower portions stated below.

Type OB 4402/100/12 is shown pictured.

OB 4301: drop indicators, iron stand.
OB 4302: drop indicators, wood casing.
OB 4401: combined jacks and drop indicators, iron stand.
OB 4402: combined jacks and drop indicators, wood casing.
OB 4501: indicator jacks, iron stand.
OB 4502: indicator jacks, wood casing.
OB 4601: visual indicators, iron stand.
OB 4602: visual indicators, wood casing.

In 1939 the OB 4XXX range was renumbered by the ABK range.  See below for more details.

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

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 10, ABK 11, ABK 14, ABK 15 and ABK 18

This range of switchboards can be found in the Ericsson Catalogue No. 610 dated 1939.  They replace the OB 4XXX range.

ABK 10 (Replaced the OB 4301)

Drop indicators, iron stand.

Model ABK 10/100/12 shown pictured.
 

ABK 11 (Replaced the OB 4302)
 

Lines	Cords	Net Weight Kg
40	7	78
50	8	80
60	9	82
80	10	86
100	12	91
120	13	96
160	16	105

Drop indicators, wooden frame.

Model ABK 11/100/12 shown pictured.


ABK 14 (Replaced the OB 4401)
 

Lines	Cords	Net Weight Kg
40	7	90
50	8	92
60	9	94
80	10	98
100	12	103
120	13	108
160	16	117

Combined jacks and drop indicators, iron stand.

Model ABK 14/100/12 shown pictured.


ABK 15 (Replaced the OB 4402)
 

Lines	Cords	Net Weight Kg
40	7	78
50	8	80
60	9	82
80	10	86
100	12	91
120	13	96
160	16	105

Combined jacks and drop indicators, wooden frame.

Model ABK 15/100/12 shown pictured.
 

ABK 18 (Replaced the OB 4601)
 

Lines	Cords	Net Weight Kg
40	7	90
50	8	92
60	9	94
80	10	98
100	12	103
120	13	108
160	16	117

Visual indicators, iron stand.

Model ABK 18/100/12 shown pictured.

 

ABK 19 (Replaced the OB 4602)
 

Lines	Cords	Net Weight Kg
40	7	78
50	8	80
60	9	82
80	10	86
100	12	91
120	13	96
160	16	105

Visual indicators, wooden frame.

Model ABK 19/100/12 shown pictured.
 

Last revised: November 24, 2025