The OL 12 is an automatic switchboard suitable for small private telephone installations of up to 10 lines.  It is designed for one conversation at a time and the conversations are secret, i. e., they cannot be overheard in telephones other than those engaged. When a microtelephone is lifted a dialling tone is sent out from the switchboard if no conversation is going on. If no diailing tone is heard the switchboard is busy.

The mechanical construction is
similar to that of OL 10 but the terminals are fitted in a junction box HM 160110 which is connected to the switchboard proper by means of a short cable.

The installation is fed from a common battery, which in view of the very small current required may be composed of dry cells of, say, 150Ah capacity.
It is of importance that the operating voltage be kept between 8 and 12 V .

A battery consisting of eight dry cells RK 224 will thus be suitable and the battery should be located near the switchboard.

The wall telephone DB 30 and the table telephone DB 200 are the only ones to be used with OL 12.

Ordinary lead covered two conductor cable, Type EEB, is used for the lines.

The lines are connected to the terminals of the junction box HM 160/10.
Regarding HM 160110 see page 39.

The telephones are given the numbers 1, 2, 3, 4, 5, 6, 7, 8, 9 and 0.

Dimensions without HM 160I10: height 256mm, width 172mm, depth 132mm, weight inch HM 160J10 4.8 kg.

Note: it is of great importance that the positive and negative poles of the battery be connected according to the diagram in the switchboard cover.

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

 

Last revised: March 29, 2024