Automatic telephone switchboard

Type OL 500

This automatic telephone switchboard is suitable for large offices, stores, banks, factories, saw mills, small municipalities etc., when the number of simultaneous conversations does not exceed 24.

This switchboard is built up of racks, on one of which is mounted all the apparatus common to the connected lines (independent of the number of these lines), and on similar racks the individual arrangements for each subscriber’s line are mounted.

These latter racks are for 50 lines each and can be easily added to an existing switchboard.
The enlargement may thus be made gradually by 10 lines at a time. It should be noted, that there will be no extra costs, when the capacity passes from two-digit to three-digit numbers i.e. from 99 to 100.
The cost for the enlargement for the lines No. 100 - 109 is the same as for the lines No. 50 - 59.
The rack for the common apparatus is normally equipped with a capacity for 24 simultaneous conversations.

When 6, 12 or 18 simultaneous conversations are sufficient, a considerable saving can be made.
Two storage batteries are required for a switchboard and arrangements for charging can be provided suited to local conditions. Prices of batteries and arrangements for charging on application.
The telephone sets, DE 100 and DE 500, which are used with this switchboard, are of the common battery type but are provided with a dial. The dial is provided with 10 numbered holes.

By means of the dial the desired connection is completed in the following manner:-
If telephone set No. 53 is required, the micro telephone of the calling set is first lifted and the tip of the finger then placed in the hole marked (5) and the dial is turned in a clockwise direction until the finger meets a stop, whereupon the finger is removed and the dial returns to normal under the influence of a spring. The same procedure is then repeated with the hole marked (3). When the dial again returns to normal, the connection is accomplished and a signal in the receiver indicates whether No. 53 is free or busy. If No. 53 is free, this telephone set is called automatically and the calling person hears a ringing tone in his receiver. If No. 53 is busy, a "busy" signal is heard in the receiver of the calling telephone.

When the conversation is finished and the two micro telephones replaced, the two lines are at once automatically released.

In such places, where it is not necessary to be able to call, but only to receive calls, common telephone sets without dial can be utilised. Such sets can also be substituted by bells or other signals if desired.

The automatic telephone switchboard is so arranged that it can by special dispositions be connected to a public telephone exchange, if this is allowed by the authorities.

In this case the public exchange is called automatically. The calls from the public exchange are distributed at the automatic telephone switchboard by an operator or any other suitable person, by means of a special switchboard, see Sheet No. 634a,showing a switchboard for 12 exchange lines (pictured to the right).


Taken from the L. M. Ericsson Telephone Catalogue No. 1921

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Last revised: October 09, 2019