| 摘要 |
PCT No. PCT/JP92/00863 Sec. 371 Date Mar. 5, 1993 Sec. 102(e) Date Mar. 5, 1993 PCT Filed Jul. 7, 1992 PCT Pub. No. WO93/01676 PCT Pub. Date Jan. 21, 1993.A ring trip deciding method in a ring trip circuit detects voltage change in the on-hook state and the on-hook state of a terminal when the terminal such as telephone set connected to the telephone line is called. The ring trip deciding circuit has a ring trip detecting resistance connected in series with a ringer generator for detecting change of current value depending on the on-hook and off-hook states, a detector for detecting voltage change across the ring trip detecting resistance, a voltage comparator for outputting different values when the threshold value is larger or smaller by comparing a voltage outputted from the detector with the threshold value, a first state latch for latching and outputting different state values depending on different output values of the voltage comparator, a composite state latch for fetching, latching and outputting at least two state values outputted from the first state latch synchronously with a clock, and a state deciding circuit for comparing state values of the composite state latch to detect the on-hook and off-hook states of the terminal.
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