APPARATUS FOR SENSING AN OFFICE LINE USAGE STATE, PARTICULARLY FOR SENSING A STATE OF AN OFFICE LINE EFFECTIVELY BY PROVIDING A RESISTOR IN A TIP LINE OF THE OFFICE LINE TO DISCRIMINATE A CURRENT FLOW IN THE RESISTOR

摘要

PURPOSE: An apparatus for sensing an office line usage state is provided to facilitate designing of a protection circuit for preventing a problem generated due to surge and thunderbolt. CONSTITUTION: A resistor(R6) is connected in series to an office line between a telephone office(2) and a terminal(1). A switching unit connected in series to one end of the resistor(R6) senses a certain current flow at the register(R6) and outputs an office line sense signal, namely, a state signal of the office line, according to the sensed current. A circuit protection unit(4) of which one end is connected to the other end of the resistor(R6) and the other end is connected in parallel to one end of the switching unit maintains the current flowing at the resistor(R6) uniformly.