| 摘要 |
<p>PURPOSE:To transmit a digital signal when the voltage of a power supply is reduced even by the small capacity of a backup power supply by separating the earth of a circuit of a microcomputer control system from that of a telephone circuit by a photocoupler. CONSTITUTION:The earth of a circuit of a microcomputer control system is separated from the earth of a telephone circuit by a photocoupler 6. When the power supply is reduced, a backup power supply 17 is connected to an encoder circuit 3 consisting of a C-MOS element of small power consumption, a selector circuit 5 and the photocoupler 6 respectively. As a result, it is possible to transmit at least the digital signal (selection signal) even though the power supply is reduced.</p> |
