Automatic circuit back-up system

摘要

An automatic circuit back-up system is adapted to a data communication system including a private communication line for data communication and a back-up communication circuit for providing a back-up for the private communication circuit. The automatic circuit back-up system includes a periodic message transmitting circuit for transmitting a periodic message at a predetermined regular period to a distant office through the back-up communication circuit, and a monitoring circuit for monitoring whether the periodic message transmitted from the distant office via the back-up communication circuit is received at the predetermined regular period.