| 摘要 |
PURPOSE:To fulfill miniaturization by changing a circuit over by a switching unit by receiving an alarm signal from each terminal equipment. CONSTITUTION:When a fault occurs in circuit A, a received fault alarm signal from the terminal station is inputted to terminal 8 and alarm receiving relay 17 is operated. Through the operation, switching transistor 18 is turned on to supply the signal to malfunction preventing FF19. After a confirmation time of 300ms passes since the occurrence of the fault, FF19 sends a signal. This signal is inputted to switching self-holding FF22, whose output state is inverted to operate circuit switching relay 14, thereby changing circuit A over to circuit B. When the circuit is changed over manually, depressing circuit-switching switches 16A and 16B puts switching transistors 18A and 18B into operation and their signals are inputted to set and preset terminals of FF22, so that the circuit is changed over. |
