step in the ordering subroutine is to compare the first and second measured values in memory b the smaller of the two is selected and compared in a successive pairwise fashion until the smallest bm of all the measurements in memory b is known since the memory location of this smallest value also indicates the channel number m from which it was taken the microprocessor looks up the code for that channel from lookup table memory a and stores that code word in the first location of order memory c that will be the first channel to be used for test transmission since ordering has not yet been completed pairwise comparison of the remaining measurements resumes to obtain the next smallest value finally after all measurement memory b locations have been ordered order memory c contains code words for the n channels to be tried in the order of increasing ambient noise level the switching operation is then begun in which the microprocessor reads code words from the memory locations in memory c providing to the frequency synthesizer the code words necessary to select specific channels in the arrangement shown in fig2 a system operation depends on the availability of independent samples of each channel the channels represent n possible frequency slots in a radio communication system wherein the synthesizer under control of the microprocessor tunes the receiver to each channel the synthesizer provides a local oscillator signal for each channel to a mixer in the receiver the receiver includes appropriate rf and if stages that translate.