PURPOSE:To prevent malfunction which generates an alarm when it is erroneously judged that a receiver is in a nonreception state owing to the interference of the signal of an oscillator, fitted to a body, with other signals. CONSTITUTION:A modulator 3 modulates a radio signal with the individual call signal read out of the individual call signal storage device 2 of the oscillation device l fitted to the body and an amplifier 3 amplifies and sends the radio signal from an antenna 6. At this time, an unfixed period generating circuit 5 gates the output signal of the amplifier 4 according to the pattern of the individual call signal and intermits the transmission output. The receiving device 7 that a user carries makes a decision in consideration of the maximum halt time of the transmission of the oscillator 1. Thus, the transmission is intermitted at random, so even when many oscillation devices 1 are used, the malfunction due to interference can be minimized.
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