| 摘要 |
Control circuit for an answering machine having an electrical unit in parallel therewith including a controller for causing a first photocoupler to be conductive for a predetermined time period to discharge a capacitor when the machine goes into an on line state and, thereafter, causing the voltage across the telephone lines to charge the capacitor via a rectifier unit; a second photocoupler for detecting a voltage drop across the telephone lines caused by picking up said unit while the machine is in its on line state while using the voltage across the capacitor as a reference, whereby the controller returns the machine to its standby state after a predetermined time from the occurrance of the voltage drop.
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