THEFT-PREVENTION SYSTEM IN PAYPHONE

摘要

The system consists of a tone generater which is connected with a public telephone (1); a detector (4) connected with communication paths (6) for detecting an input tone frequency and generating a logical signal according to the tone frequency; a clock generator (5) connected with the detector (4) to supply a synchronizing signal to it; a switching means (3) connected between the communication path and an exchange (7) to operate ON/OFF by a output logical signal of the detector (4).