A duplex interphone wherein a master station and substation each having a microphone and a receiver are interconnected through two exclusive communication lines. The audio signal produced by the microphone in the master station is transmitted through said two communication lines in the form of a modulated carrier signal or audio signal. The audio signal produced by the microphone in the sub-station, on the other hand, is transmitted through said two communication lines in the form of a modulated carrier signal or audio signal having a different frequency band than that of the signal transmitted from the master to sub-station. The transmitted audio signal or the audio signal derived by demodulating the transmitted modulated carrier signal is used to drive the receiver in the master station or sub-station.
A residential phone system allows for local control of call features from any phone extension. The phone system may include a microcontroller that communicates along the phone lines at a non-utilized frequency to several extension phones in a residence. The microcontroller permits each phone to control call features such as call waiting, conference calling, paging, or other features. A control box may be included at any or all of the extension phones to provide a convenient user interface to access the call features.
A residential phone system allows for local control of call features from any phone extension. The phone system may include a microcontroller that communicates along the phone lines at a non-utilized frequency to several extension phones in a residence. The microcontroller permits each phone to control call features such as call waiting, conference calling, paging, or other features. A control box may be included at any or all of the extension phones to provide a convenient user interface to access the call features.
An intercom system for use in combination with a multi-line telephone system wherein the intercom system utilizes the same wire pair for communications between intercom units that is used for normal telephone communications. The intercom system transmits voice signals on two or more frequency modulated channels over a wire pair of a local telephone network. Each intercom unit includes a microprocessor which controls communication activity and protocol in each unit and communicates with other intercom unit miroprocessors via a separate frequency modulated digital signal channel.
