A tone detector able to detect multicomponent tones for various tone
formats is disclosed. An input signal is received and frequency and
amplitude components, if any, of each sample of the incoming signal are
estimated. In estimating the components, a current digit value is used to
appropriately filter the input signal and estimate frequency and
amplitude components. Using the component estimates, a new digit value is
determined using a table in storage corresponding to the current tone
format. The new digit value corresponds to the symbol whose components
are closest in value to the estimated components corresponding to the
current digit value. The new digit value is fed back as the current digit
value and used in combination with a next sample of the input signal to
determine a new digit value. A decision unit is used to process the digit
values to determine when a valid symbol is detected.