| 摘要 |
PURPOSE:To prevent a mischarging based on the misidentification, by stopping the oscillation by a circuit consisting of the transistor, NAND circuit and others in case a fault arises at the transistor that receives a temporary off-control for identification of the party line subscriber and accordingly a misidentification is caused. CONSTITUTION:Either the party line subscriber A or B has an off-hook, and thus the output of the hook detecting circuit DET is set at ''1''. Then the output of the NAND circuit G1 is set at ''0'' in the timing of the subsriber position pulse (a), and ''0'' is added to the party line subscriber identifying circuit IDT. The circuit IDT sets the signal (b) at ''1'' to set the FF. In this case, if the transistor Q1 is normal, the transistors Q1 and Q2 are turned off with Q4 turned on by the output of ''1'' of the terminal Q. As a result, the output (d) of the NAND circuit G2 is set at ''1'' although the terminal Q is set at ''1''. If the subscriber A has an off-hook, the output of the circuit G1 is set at ''0'' since the Q2 is on. When the subscriber B has an off-hook, the output of the circuit G1 is set at ''1'' since the Q2 is off. Thus the circuit IDT can identify (which) subscriber A or B had an off-hook. |
