| 摘要 |
<p>A telephone call control device comprises a casing (1) for attachment to the housing of a freely accessible telephone socket, a control plug (15) carried by the casing for engaging in the telephone socket when the casing is attached, a control socket (21) carried by the casing for receiving the plug of a communications apparatus to be connected to the telephone socket, and control circuit means in the casing for electrically connecting the control socket and the control plug. The control circuit has a call-restricting operating condition in which, following dialling from an apparatus connected to the control socket, the control circuit monitors the transmission on the line and, in the absence of a predetermined carrier signal, disconnects the line.</p> |
