The system is centralized, meaning that the various stations call a central location that is serviced by an operator.

The subscriber calls the operator by turning the telephone's crank generator. The operator responds from the central location and asks who he or she wishes to call. At the central location, there is an impulse sender (key) for each telephone station. Each key is set with an individual impulse combination. When the operator calls a subscriber by turning their key, the subscriber's impulse combination is sent. This always consists of 17 impulses. For example, Åsaka has 2-2-13, Banvaktsstugan has 3-6-8, and Bäreberg has 5-8-4.

At all telephone stations, the relays (selectors) now operate. The phone rings only at the subscriber where the impulse combination matches the selector’s setting. At other subscribers, the selectors return to the home position (default state).