The presence of a supervisory audio tone signal (SAT), superimposed on a voice/data signal transmitted in a cellular telephone system, is carried out by first deleting the voice/data signal, leaving only the SAT signal. Thereafter, the SAT signal power and noise power are determined. During intervals when the SAT signal rises and falls, the SAT noise power and signal power move in opposite directions when the radio carrier turns on and off, respectively. By comparing the SAT noise power to the SAT signal power, a fast, accurate determination can be made as to whether the SAT signal is present. Moreover, the ratio of the SAT signal power to SAT noise power provides a good estimate of the quality of the channel in the cellular telephone system. By repeatedly computing the SAT signal power to noise power ratio, a base station (48) in the cellular telephone system can decide when to hand off, and to which other base station such hand-off should be made.

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