| 摘要 |
PROBLEM TO BE SOLVED: To match with the various kinds of demands by the programming of a telephone subscriber loop interface (SLIC) by a user by applying a first variable voltage corresponding to a control current in the case that a detected current is the same as reference currents on an upper side and a lower side or is between the reference currents. SOLUTION: A resistance element Rloop54 is used for the detection of a current flowing through a subscriber line 34. The resistance elements Rlim, Rd, Roh and Rde are selected so as to independently set a current limit, an overhead, resistance power feed and a switch hook detection threshold. A first voltage level for indicating an on-hook state is applied when the current detected in a voltage control means for applying a voltage to a terminal is less than the reference current on the lower side, a second voltage level for indicating an off-hook state is applied when the detected current is more than the reference current on the upper side and the first variable voltage is applied corresponding to the control current when the detected current is the same as the reference currents on the upper side and the lower side or is between the reference currents. |
