| 摘要 |
<p>PURPOSE:To transmit the information at power failure to a master station with batteries of small capacity, by providing a signal tone transmitter of the frequency other than the data transmission frequency zone and the battery to a slave station, in a data transmission system between the master station and a plurality of remote slave stations. CONSTITUTION:When a commercial power supply is applied to a slave station 21, switching relays 14a, 14b are switched to a modulation and demodulation device 7 side and the side cutting off the power supply to a tone transmitter 12, and the information is fed from a data processor 8 to a mater station 1. When the commercial power supply is in failure in a slave station, the relays 14a, 14b are respectively switched to the tone transmitter 12 and the battery 13, and the signal tone of the transmitter 12 is fed to the master station 1. The signal tone frequency of the transmitter 12 is selected outside the usage band of the device 8, this signal is received at a tone receiver 151 of the master station 1, and the master station konws the power failure of the slave station 21. In this case, since the battery 13 of the slave station can only have the capacity to operate the transmitter 12, the device in the slave station can be made small in size.</p> |
