Limitation of charges incurred by unauthorised telephone connection - opening isolating switch operated by countdown to expiry of time limit for local, national or international call.

摘要

The method involves determining a distance of a destination with a dialling evaluation unit (WA) using input dialling digits of dialling information (WI) for the evaluation. Dialling information is loaded from a read-only memory (ZSP) storing corresp. unit charging intervals into a timing counter (ZZ) decremented by a clock (ZT) from a control unit (SE). An attention signal (AZ) is sent to an earpiece (H), loudspeaker (L) or optical display (AE). The counter may also be decremented by charging pulses (GI). ADVANTAGE - Disconnection is effected automatically and irrespective of presence of charging pulses, esp. when there is no reply. Connection can be perpetuated when necessary on sufficient grounds.