Importance

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Abstract

A 'wireless' door answering intercom system (meaning no special wiring between the inside and outside stations) that allows a visitor to carry on a two-way conversation with a person inside the building without requiring the visitor to manipulate a 'push-to-talk' button. The transmitter and receiver at the outside door are on all the time, powered by connections to the existing A.C. power system in the building. The outside transmitter and receiver operate on separate carrier frequencies or frequency bands, the receiver on Channel 1 and the transmitter on Channel 2. The inside answering station includes a transmitter on Channel 1 and a receiver on Channel 2. The inside station has a spring loaded 'push-to-talk' switch. This switch is normally biased to connect the inside answering station speaker/microphone to the output of the Channel 2 receiver, so that anything said at the outside door station can be heard at the inside answering station. When the 'push-to-talk' switch is pushed, it connects the inside loudspeaker to the Channel 1 transmitter, and the speaker functions as a microphone, so that whatever is said at the inside answering station is heard at the outside door station.

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First Claim