Abstract: An amplifier in a housing for receiving and detecting the presence of portable paging devices that produce an audible signal when activated. The amplifier allows the connection of a large capacity annunciator or visual alarm. Circuitry is provided to connect the output of the amplifier to the bell of conventional telephone sets without affecting its normal operation. The telephone set bell can be activated with a voltage signal different from the one it normally generates so that a user can distinguish the two calls.