CROSSTALK DETECTING SYSTEM OF COMMUNICATION CIRCUIT

摘要

PURPOSE:To prevent the wrong detection of a crosstalk with a crosstalk detector which detects the earth or a battery of a communication circuit to perform the crosstalk detection, by discontinuing the switch of connection between the communication circuit and the earth and the battery when a crosstalk is detected to hold the crosstalk detection state and deciding a crosstalk if the crosstalk duration exceeds a fixed period of time. CONSTITUTION:A crosstalk detecting circuit 6 transmits a periodical switch stop signal 10 after receiving an earth crosstalk detecting signal 8 or a battery crosstalk detecting signal 9 and stops the periodical switch to hold the crosstalk detection state. At the same time, the circuit 6 transmits a deciding timer start signal 11. A deciding timer circuit 7 is started by the signal 11 to monitor the crosstalk or handset pick-up duration. The time value exceeding the duration of a crosstalk state that is produced by a temporary pick-up of handset is set to the circuit 7. Therefore the circuit 7 transmits a crosstalk deciding signal 12 when the duration of the crosstalk state exceeds said time value. This signal 12 is used to display an alarm for a crosstalk fault and to control the incoming to a telephone type terminal.