Method of determining levels at given frequencies of a VF signal

A dialing receiver for determining multifrequency dialing signals on an incoming signal in a telecommunication switching system, comprising;

• A) a sampling circuit for taking N values of the incoming signal N times at a given sampling rate, where N is a positive integer;
• B) a zero value generator circuit for supplementing at the given sampling rate the N values with M successive zero values so as to yield N+M values, where M is a positive integer;
• C) a discrete Fourier transformation circuit for performing a discrete Fourier transform (DFT) of said N+M values in accordance with a Goertzel algorithm and providing a result in form of a series of Fourier coefficients;
• and
• D) a result evaluating circuit for directly evaluating the results of the discrete Fourier transform (DFT) processing of the N+M values without interpolation so as to determine an identity of the multifrequency dialing signals.

Method for identifying at least one given frequency in a multifrequency signal in a dialing receiver, comprising, in combination, the steps of:

• sampling the multifrequency signal in a sampling circuit at a sampling frequency and generating N samples;
• generating in a zero value generator M samples having a value of zero;
• receiving the N samples and the M samples in form of a finite duration sequence of length N+M in a discrete Fourier transformation computation circuit, transforming successively said sequence with a discrete Fourier transform using a Goertzel algorithm, and generating a series of discrete Fourier coefficients;
• evaluating in a results evaluation circuit the presence of said at least one frequency of the multifrequency signal based on an absolute value of said coefficients at a given frequency without using interpolation between coefficients being evaluated and generating an output signal indicating presence of absence of said at least one frequency.