| 摘要 |
PURPOSE:To realize the signal tone trunk less in component number, of small in size and economical, by forming the interrupting information of signal tone to be delivered with the logic circuit in the signal tone trunk. CONSTITUTION:The signal tone trunk TRK is connected to the subscriber via the communication path, the delivery instruction of required signal tone is received, and signal tone is delivered to the subscriber. The logic level signal ''1'' is fed to one input Po of the AND circuit 5 and the interruption signal formed with the interruption circuit INT is fed to another input. When the input Po of the path 5 is at ''1'', TrQo repeats ON and OFF 240 times per minute via the OR circuit 8, allowing to repeat conduction and non-conduction of diodes Doo and Do1. The continuous AC signal is formed as the signal tone of special call tone SDT and it is delivered to the subscriber via communication line. The logic level signal ''1'' fed to the input Po of the path 5 is taken to ''0'', making TrQo diodes Doo and Do1 interruptive and stopping the signal tone. |
