DIAL PULSE DETECTION SYSTEM

摘要

PURPOSE:To prevent the transient vibration current from being detected erroneously as the dial pulse, by securing an automatic setting of the threshold level corresponding to the dial pulse level. CONSTITUTION:The current flowing between the telephone and the exchange is detected through circuit 1 and then memorized in current value memory circuit 2 at least for the dial pulse receiving period. This memory contents is added to threshold level control circuit 3 to control the threshold level at threshold level circuit 4 where the dial pulse is detected. Then delay switching circuit 5 resets the circuit after end of the dial pulse reception to get ready for reception of the next dial pulse.