Method and apparatus for determining an optical communications channel without loss of channel messages on a current communications channel

A method for operating a portable radio comprising the steps of:

• (a) monitoring a current radio communications channel which is divided into a series of frames with each frame including a first field of synchronization bits and a second field of message bits, the second field including a first message followed by other information;
• (b) after the first message, scanning another radio communication channel;
• and
• (c) returning to the current communications channel by or before the start of a next frame in the series of frames.

A method for operating a portable radio comprising the steps of:

• (a) obtaining synchronization with a first digital radio channel which is divided into a series of frames with each frame including a first field of synchronization bits and a second field of message bits, the second field including a first message followed by other information;
• (b) after the first message, tuning to a second digital radio channel;
• (c) determining a fidelity of a signal received on the second digital radio channel without obtaining synchronization with the second digital radio channel;
• and
• (d) returning to the first radio channel.

A method for determining the fidelity of a digital signal received over a digital communications channel, comprising the steps of:

• (a) receiving a digital signal on the digital communications channel including a number of digital bits corresponding to a message;
• (b) sampling each received bit in the message N times at N corresponding sampling intervals, where N is a positive integer;
• (c) comparing sets of sample values obtained at corresponding ones of the sampling intervals to an expected set of values for the received bits;
• and
• (d) summing the total number of times when the compared sets of sampled values match to generate a fidelity indicator for the digital communications channel, wherein a larger total number indicates higher signal fidelity.

A radio communications system comprising:

• a plurality of RF repeater sites, each site having a control channel repeater and a plurality of working channel repeaters;
• and
• a plurality of portable radios each of which monitors a selected control channel of one of the plural sites, the control channel being divided into time slotted frames, each radio including:
• a receiver for receiving plural messages per frame over the selected control channel with each message corresponding to one time slot, and
• processing circuitry for performing the following tasks:
• detecting a first message in one time slot of a frame over the selected control channel,
• determining the fidelity of one or more alternative control channels during remaining time slots in the frame, and
• returning thereafter to the current communications channel by or before the time the next frame is to be received by the receiver.

A system for determining the fidelity of a digital signal received over a digital communications channel, comprising:

• a radio receiver for receiving a digital signal including a number of digital bits corresponding to a message;
• and
• electronic circuitry for performing the following tasks:
• (a) sampling each received bit in the message N times at N corresponding sampling intervals, where N is a positive integer;
• (b) comparing sets of sample values obtained at corresponding ones of the sampling intervals to an expected set of values for the received bits;
• and
• (c) summing the total number of times when the compared sets of sampled values match to generate a fidelity indicator, wherein a larger total number indicates higher signal fidelity.