| 摘要 |
PURPOSE:To make the formation of a channel loop easy, through the detection of a polarity inversion signal with a channel loop relay controlled and driven by the sure detection of incoming signal at electronic circuits such as a photocoupler and a counter and the like. CONSTITUTION:An incoming signal switched with a contact of a hook switch HS provided in a polarity inversion channel from an exchanger is applied to a light emitting element D5 of a photocoupler PC and an optical signal of the element D5 is detected at a photodetector Q. The outut from the element Q is applied to an electronic circuit consisting of a capacitor C3 and resistors R4 and R5, and when a pulse of a prescribed pulse width is supplied with the output of the electronic circuit, a detection signal of a polarity inversion signal is outputted from a charge/discharge circuit DL1. The output of the element Q is counted at a counter CT and an incoming signal from a channel circuit TC is outputted from an OR gate OR when the counts reach a prescribed number. Contacts l1-l4 of a channel loop relay provided at the pre-stage of the circuit TC are closed to form a channel loop. |
