| 摘要 |
PURPOSE:To realize an automatic camp-on for the reset call system of the key telephone system by giving redialing without hooking the handset even under the busy state of the extension calling and thus resetting the counter circuit first at the beginning of the redialing. CONSTITUTION:With push-on of the extension key, terminal P2 becomes the (+) potential. Then transistor TR2 is turned on via diode Da plus resistance R1 and R2 to turn the output of B-position circuit BP to the L potential. With dialing the pulse is sent to dial counter citcuit for counting and memorization via TR2, inverter 1 and AND gate 2 each. When the dialing ends, output Q of flip-flop 5 features the H potential. Under the busy state, output Q of flip-flop 3 is also kept at the H potential. With the second dialing, the output of NOR gate 8 becomes the L potential. And thus flip-flop 5 and dial counter circuit CT are reset. |
