An Infra-Red Wireless Speaker System Utilizing a Super Wideband FM Carrier

In a Quadraphonic Hi-Fi system it would be highly desirable that the two rear speakers be wireless. The two rear speakers would be completely independent from the main unit and would be composed of a receiving system, power amplifier and speaker. A short range communication system is needed that has full Hi-Fi performance; a bandwidth of 50 to 15 KC signal-to-noise ratio greater than 60 dB and total harmonic distortion of less than 1%. Also, the cost of the system should be as low as possible. There should be no interference between the two rear speakers or with a neighboring system in a nearby room. It would be desirable that the volume level and balance of the whole system could be accomplished at the main unit. This would necessitate that each of the rear speakers also have a remote volume control function. This may be accomplished in two manners. A special control signal may be sent to each of the rear speakers where it will be decoded and set the volume level of that speaker; or, the signal-to-noise ratio of the system can be raised sufficiently high so that the power amplifier can be operated at full volume and during a quiet passage no background noise be heard in a quiet room. A signal-to-noise ratio of approximately 85 dB would be needed.