"Plug and play" telephone system
Collective-house control system employing an interface circuit f
Device for communicating a doorside intercom set with a remote t
Door intercom
Electronote wall mounted messaging device
In-line telephone intercom system
Intercom system
Intercom system for a service establishment
Intercom telephone
Key telephone apparatus
Key telephone system
Key telephone system with distributed control
Method and apparatus for designating and making an automatic cal
Method and apparatus for interfacing a drive-thru intercom...
Method and apparatus for recording or forwarding messages
Microprocessor controlled telephone unit
Multiplexed data channel controlled telephone system
Network-based intercom system and method for simulating a...
Network-based intercom system and method for simulating a...
Play and plug telephone system