| 摘要 |
<p>There is disclosed herein a telephone circuit for generating a ringing rhythm and for off-hook detection, which is able to interface a subscriber line and a subscriber line circuit under the supervision of the control units of an exchange; when these order the telephone circuit to send a ringing signal, it generates the ringing rhythm, in order to drive a relay capable of interconnecting the subscriber line and a ringing current generator, and it interrupts the ringing rhythm when, due to off-hook, the positive half-periods of the ringing current have a duration that differs in a predetermined degree from the duration of the negative half-periods.</p> |
