PURPOSE: To improve reliability by discriminating between an alarm signal and a diagnostic signal for the periodic transmission from a received security signal, thereby hardly occurring the malfunction of system.
CONSTITUTION: When a sensor appended to the system outputs an abnormal signal, a signal processing section 3 is operated to immediately start a supervise timer circuit 2 and to start a from end section 1. A security signal fetched with the alarm signal as data is transmitted from antenna 1a. On the other hand, the supervise timer circuit 2 operates the front end section 1 in the period set in advance to perform the periodical transmission. In this case, the diagnostic signal is transmitted to a signal code generation circuit 4, thereby security diagnostic signal as data are generated. In this case, the alarm signal at the time of occurring abnormality and the diagnostic signal for the periodical transmission are discriminated by changing the combination of two bits in the data.
NAKAJO HIROSHI
MURAO SEIJI
OKADA HIDEAKI
