Hold-plus-intercom for single-line stations
Modular, expandable intercom system for a multiple-station telephone subscriber installation
Tone selective key telephone intercom system including digital tone detector
Home communications and control system
Key telephone system
Telephone intercom system
Programmable telephone switcher Patent #: 4674115
ApplicationNo. 07/045321 filed on 05/04/1987
US Classes:379/393, Hold circuit379/160With connection of intercom station to subscriber line
ExaminersPrimary: George, Keith E.
Attorney, Agent or Firm
International ClassesH04M 1/72 (20060101)
H04M 1/723 (20060101)
H04M 9/02 (20060101)
AbstractA device for adding intercom functions to a residential or small business phone system uses existing telephone equipment and wiring. The device attaches to the incoming telephone line to switch telephone calls and generate user coded ringing signals. The invention allows the user to simultaneously use existing telephone equipment as an intercom system and for normal outside telephone use.