Alarm and test system for a digital added main line
Apparatus for hands-free operation of a mobile telephone unit in
Beeper amplifier
Building entrance telephone terminal box
Connecting a telephone
Dual-line telephone jack adapter and cable coupler
Electronic switching system
Interface device between a public telephone and an external term
Modem interface device
Modular jack having built-in circuitry
Multipurpose headset amplifier
On-line indicator for multipurpose headset amplifier
Shunted modular jack
Telephone handset interface for device having audio input