Patent ID: 7127060

Claim:
A subscriber circuit, provided with a feeding circuit for feeding current of a call to a terminal through a subscriber line and a switching circuit group for connecting the feeding circuit to the subscriber line and releasing the feeding circuit from the subscriber line, for controlling feeding to the terminal, comprising: said feeding circuit monitoring state of a loop of the subscriber line, converting a two-wire signal sent from the terminal into a first signal predetermined coefficient-fold, and outputting the first signal predetermined coefficient-fold; a level converter, connected to the subscriber line through said switching circuit group, which converts a two-wire signal sent from the terminal into a second signal predetermined coefficient-fold and outputs the second signal predetermined coefficient-fold, separately from said feeding circuit; a signal output circuit which receives the output signal of said feeding circuit and the output signal of said level converter and which outputs one of the signals, a wave filter which filters the output signal of said signal output circuit, a signal monitor which monitors a signal based on the output signal of said wave filter and supplies signal monitor information, and a control circuit which controls connection and disconnection by said switching circuit group, output of said feeding circuit, output of said level converter, and operation of said signal output circuit, depending on the operation, according to upper control information and the loop monitoring output of said feeding circuit, wherein said control circuit connects said feeding circuit to said switching circuit group and connects said level converter to said switching circuit group when said terminal is in an on-hook state, and wherein said control circuit connects said feeding circuit and said switching circuit group and disconnects said level converter from said switching circuit group when said terminal is in an off-hook state, and wherein loop monitoring information provided by said feeding circuit is not provided to said control circuit when said feeding circuit is disconnected from said switching circuit group.