| 摘要 |
PURPOSE:To reduce the current consumption of a radio terminal station device at standby by changing over a power supply at DC loop detection and a power supply after the detection to use as a power supply supplying a DC loop detecting circuit at the radio terminal station device. CONSTITUTION:When a telephone set 5 is in on-hook state at the standby, a DC loop is in the state of interruption, a power supply (13.8V) supplied to the radio terminal station device is used and a voltage of 13.8V is supplied to the telephone set 5 via a switching circuit 9, a loop detecting circuit 10 and an interface circuit 11 from a power supply 7. A DC-DC converter circuit 8 is stopped in this case. When the telephone set is hookd off, a DC loop is constituted, the detecting circuit 10 detects a DC loop and transmits a control signal to a converter 8 and the switching circuit 9 to start them and the power supply is changed over from the power supply (13.8V)7 to a voltage (48V) boosted by the converter 8. Since the converter 8 is stopped at the standby, the current consumption is reduced. |
