초록 ▼

An ultrasonic communication system capable of wireless installation and supervised operation is achieved by communicating each information bit as two distinct ultrasonic frequencies separated in frequency enough to assure that the signal strength of both transmissions will not be in a deep null at t

An ultrasonic communication system capable of wireless installation and supervised operation is achieved by communicating each information bit as two distinct ultrasonic frequencies separated in frequency enough to assure that the signal strength of both transmissions will not be in a deep null at the receiver location at the same time. The transmissions can be coded with a format that recognizes the correct data transmission even if reception of one frequency is lost. By use of transponders and other auxiliary units with periodic polling, supervised operation throughout a building can be maintained with events such as intrusion, fire or emergency as well as failures of particular units of the system reported.

대표청구항 ▼

A wireless data communication system operable to transmit information as ultrasonic frequency signals which are subject to loss caused by nulls due to multipath signal cancellation at a receiving station comprising: a plurality of spaced stations capable of transmission and reception at a plurality

A wireless data communication system operable to transmit information as ultrasonic frequency signals which are subject to loss caused by nulls due to multipath signal cancellation at a receiving station comprising: a plurality of spaced stations capable of transmission and reception at a plurality of different ultrasonic frequencies sufficiently separated in frequency to spatially separate the respective locations of nulls of said different frequencies due to multipath propagation between communicating stations; means for transmitting said information by modulating each of said ultrasonic frequencies with the same data bits and transmitting each said data bit at said different ultrasonic frequencies; and ultrasonic receiving means at each receiving station for recovering said data bits by detection of any one or all of said ultrasonic frequencies.