| 摘要 |
PURPOSE:To stably supply electric power to a data line terminating device unlimitedly in time even when a power failure takes place at the place where the device is installed and, at the same time, to suppress an increase in the cost of the device by supplying the device with the secondary power supply of a local power source circuit at the normal time and secondary power supply of a remote power source circuit at the time of the power failure. CONSTITUTION:A feeder circuit 32 provided to a data line terminating device 30 supplies a constant current to a subscriber's line 33 and a local power source circuit 41 provided in another data line terminating device 40 generates secondary power supply upon receiving primary power supply at its installed place. A power failure detection circuit 42 detects the power failure of the circuit 41. The constant current from the circuit 32 is supplied to a switching circuit 44 through the line 33 and is closed only when the circuit 42 detects the power failure. Upon receiving the constant current when the circuit 44 is closed, a remote power source circuit 46 generates secondary power supply and a power supply circuit 43 supplies the secondary power supply from the circuits 41 and 46 to the main circuit section 45 of the device 45. Therefore, stable power supply can be made unlimitedly in time to this data line terminating device even when a power failure takes place at its installed place and, at the same time, the scale of the circuit 32 can be reduced, resulting in cost reduction. |
