Digital voter for multiple site pst r trunking system

Abstract

A digital voter system for a multi-site public service trunking (PST) digitally trunked RF communications system operates on the principle that it is highly likely that messages received during a system redundancy removal period are redundant messages. For a given RF channel, digital receiver is associated with each of multiple sites and receives digital messages reported to it by its associated sites. The multiple digital receivers are connected to a digital selector via a service request line (FSL) and a serial data line (BSL). Digital receivers which have messages to transfer to the digital selector attempt to seize the service request line and, if they successfully seize it, maintain the line in its seized state for the redundancy removal period. Digital receivers which have messages but discover the service request line is already seized simply discard their messages. Since it is likely that two digital receivers may successfully seize the service request line at or near the same time, a windowing technique is used to schedule the times different digital receivers may apply their messages to the serial data line. If a digital receiver sees signals on the serial data line before it is scheduled to begin transmitting, it discards its message and aborts its transmission attempt. The preferred embodiment voter thus handles messages very rapidly (to reduce system latency time) while effectively removing most redundant messages and reducing or eliminating data collision on the shared serial data bus.