Improved receiver selecting (voting) system

Abstract

An improved receiver voting system is disclosed in which the lowest noise audio signal produced by a number of different radio receivers is selected and coupled to a monitoring speaker. Each receiver receives signals from a transmitter and produces either corresponding audio signals or squelch indicating status tones which are then transmitted to a voting (selecting) control center by telephone communication lines. The voting control center then selects the unsquelched receiver audio signal having the lowest noise level and couples this signal to a monitoring speaker. The voting center indicates which receiver is supplying the selected signal and therefore identifies the most favorable receiver to transmitter signal path. Parallel squelch circuits in each receiver provide for the initial selection of the strongest received signal while preventing the existence of an irratating 'squelch tail.' Automatic gain control circuitry in the voting control center compensates for loss variations between the different transmission lines coupling signals to the voting control center. Status tone decoders in the voting control center prevent the selection of the squelch indicating status tone as the receiver signal having the lowest noise level. The voting control center has circuitry for switching in a status tone notch filter and changing the response time of the status tone decoder whenever a squelch indicating status tone is anticipated by the control center. Each receiver produces an audio pause which precedes the production of a squelch indicating status tone, and this enables the voting control center to anticipate the status tone and to rapidly respond to its occurrence.