Abstract: For use in a channel synthesizer utilizing a pulse swallowing phase locked loop, an eight bit code represents the megahertz component of the selected channel. An eight stage shift register is preloaded with the coded version of the selected megahertz component, and exclusive OR logic responsive selectively to the first, third, fifth, and eighth stages generates data for the first stage during the next shift. NAND logic responsive to the various stages detects presence of certain code combinations which are representative of terminal count states. Each terminal count pulse is utilized for comparison with the frequency reference in the phase locked loop, and also in a feedback arrangement to reset the registers to their preloaded states.

Abstract: A voltage controlled oscillator in a phase locked loop generates signals through the avionics communication band, and the VCO output is divided alternately by first and second factors corresponding to kilohertz range increments, and then by a third factor corresponding to the applicable megahertz increment. The relative time periods during which the respective KHz factors are utilized depends upon the count generated by a logical circuit, operating responsively to encoded representations of channels to be utilized. First and second preloaded counters operate for a predetermined time period, during which both factors are utilized alternatively; during the remainder of the counting cycle, only one factor is utilized.

Abstract: In a radio synthesizer adapted for use in an aircraft transceiver, an out of lock detector which enables or inhibits output from the synthesizer depending upon whether the synthesizer phase lock loop is in or out of lock. Under normal in lock operating conditions the oscillator output is coupled to the input of an output amplifier. When the loop is out of lock, pulse signals are generated at the loop phase detector and peak integrated to produce a signal which inhibits transmission of the oscillator output to the output amplifier, so that no output is produced while the synthesizer searches for a selected frequency.