US 5,315,639 A · Hands-free intercom system

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.

A wireless intercommunication system that permits a person at a calling station at a predetermined location to use the system without operating a push-to-talk switch, which system is utilized with a conventional electrical power line that provides electrical power at a standard frequency at a plurality of outlets, one of which outlets is located in the vicinity of the predetermined calling station and one in the vicinity of an answering station, which wireless intercommunication system comprises:

(a) a predetermined calling station, which includes:
(i) means for delivering alternating electrical current at a standard frequency to said predetermined calling station from said outlet in the vicinity of the calling station;
(ii) a radio frequency receiver whose input leads are connected across said means for delivering alternating electrical current, said receiver operating on a first predetermined carrier frequency or frequency band as a part of a first sound transmitting channel;
(iii) a loudspeaker operatively connected to the output of said radio frequency receiver for said first channel;
(iv) a radio frequency transmitter whose output leads are connected across said means for delivering alternating electrical current, said transmitter operating on a second, separate, predetermined carrier frequency or frequency band as a part of a second sound transmitting channel;
and
(v) a microphone operatively connected to the input leads of said radio frequency transmitter for said second channel;
and
(b) an answering station, which includes:
(i) means for delivering alternating electrical current at a standard frequency to said answering station from said outlet in the vicinity of the answering station;
(ii) a radio frequency transmitter whose output leads are connected across said last mentioned means for delivering alternating electrical current, said transmitter operating on said first predetermined carrier frequency or frequency band as a part of said first sound transmitting channel, said transmitter having one input lead connected to ground;
(iii) a radio frequency receiver whose input leads are connected across said last mentioned means for delivering alternating electrical current, said receiver operating on said second, separate, predetermined carrier frequency or frequency band as a part of said second sound transmitting channel, said receiver having one output lead connected to ground;
(iv) a speaker/microphone adapted to operate as a microphone when operatively connected to said transmitter for said first channel and as a speaker when operatively connected to said receiver for said second channel, said speaker/microphone having one lead connected to ground;
and
(v) talk/listen selection means which:
has at least one talk position and at least one listen position,
is normally biased from a talk position to a listen position to connect the second output lead of said receiver for the second channel to the second lead of said speaker/microphone, and
when moved into a talk position by the person at said answering station, is adapted to connect the second input lead of the transmitter for the first channel to the second lead of said speaker/microphone,
whereby the person at the predetermined calling station can communicate "hands-free" with the person at the answering station, since;
the receiver for the first channel and the transmitter for the second channel, both located at the predetermined calling station, are operative at all times,
one or the other of the transmitter for the first channel and the receiver for the second channel, both located at the answering station, is selectively operative depending upon the position of the talk/listen selection means at the latter station,
said talk/listen selection means, when in a normally biased listen condition, connects the speaker/microphone at said answering station to the output of the receiver for said second channel, so that any sound picked up by the microphone at the predetermined calling station will be converted by it into an electrical signal in the audio frequency range, which is then converted by the transmitter for the second channel into a radio frequency electrical signal that is carried by said conventional electrical power line to the answering station and converted there by the receiver for the second channel and the speaker/microphone into an audible sound, and
the reverse is true when the talk/listen selection means is actuated by the person at the answering station to connect the speaker/microphone to the second input lead of the transmitter for the first channel.

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Hands-free intercom system

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Hands-free intercom system

Life of this patent

Abstract

Claims12