| 摘要 |
<p>An amplifier (10) in a housing (20) for receiving and detecting the presence of portable paging devices (B) that produce an audible signal when activated. The amplifier (10) allows the connection of a larger capacity annunciator or visual alarm (35). Circuitry (40) is provided to connect the output of the amplifier (10) to the bell of conventional telephone sets T without affecting its normal operation. The telephone set T bell can be activated with a voltage signal different from the one it normally generates so that a user can distinguish the two calls.</p> |
