| 摘要 |
PURPOSE:To make it possible that a high order station monitors power-off of a commercial power source of a low order station, by transmitting a tone signal from a radiotelephony device of the low order station at intervals of a certain time while the commercial power is supplied. CONSTITUTION:When the commercial power source is turned on, a radio-telephony device 2 of the low order station transmits a tone signal fB to a radiotelephony device 1 if the high order station at intervals of a certain time (a) by a tone signal generating circuit 3. The high order station 1 detects the signal fB by a tone signal detecting circuit 4 to reset a timer circuit 5, which is operated by a preliminarily set time, at a time (d). If the commercial power source of the low order station 2 is turned off at a time (e), the timer circuit 5 is not reset because the signal fB is not transmitted. Therefore, low order station commercial power turn-off information (g) is outputted from a monitor information output circuit 6. |
