| 摘要 |
<p>The object of the device is to monitor telephone calls coming through a subscriber station before they are transmitted to this station. It comprises switching means (RL1, RL2, RL3) aimed at being connected to the subscriber line, reception and detection means (RF1, RF3, RF5) of a coded sound frequency signal transmitted by the subscriber line and control means for controlling the switching means, associated to the detection means altogether assembled so as to connect the subcriber line to the station after reception and detection of the coded signals. The device is aimed at being connected on any subscriber station. </p> |
