Radio voice communications system - has fixed central station selecting signal with lowest noise level from fixed receivers at different locations

摘要

The radio voice communications system, e.g. for vehicles, has a fixed central station with one transmitter and two or more radio receivers at different places. A comparator at the central station determines which received signal has the least noise by comparing auxiliary signals passed from the two or more fixed receivers. These auxiliary signals describe the noise present in the signals received by the receivers from a vehicle. Each fixed receiver has an auxiliary-signal generator producing a d.c. output voltage inversely proportional to the noise level at that receiver. The comparator automatically determines the largest d.c. voltage and selects the demodulated radio signal associated with it.