Remote warning system for protection against vandalism - uses detectors at protected location linked via automatic dialling telephone to monitor position

摘要

The remote warning system provides warning at a central position by sending warning signals via the telephone network. A variety of sensors may be used to detect the presence of a person - pressure cable in the ground, and vibration detectors for example. In the case of a telephone booth, a timing device may initiate an alarm signal if a booth is occupied, but no call is made within a set time. The sensors are connected via interfaces (2) to a carrier signal generator (3). An automatic number dialling circuit (4), a tone detection circuit (6) and start and end of message circuits (7,8) contribute to the generation of a warning signal on the output telephone line (13), when an alarm condition is detected. The end of message detector provides a return-to-zero signal after a warning message has been transmitted.