Abstract: A method of calculating the fast Fourier transform or the inverse fast Fourier transform of a series of N real samples x(n), with N power of two, operating according to a time interleaving algorithm and providing the sample series X(n) in ascending order to index n and using limited calculating storage means. A method of calculating the fast Fourier transform or the inverse fast Fourier transform of a series of N conjugated complex samples X(n), with N power of two, operating according to a frequency interleaving algorithm.

Abstract: This test equipment permits a testing of the demodulator of a teletex television receiver. It consists of a digital test signal generator, the output of which is connected to the HF input of the television, and a receiver, the input of which is connected to the video output of said receiver. The generator tramsmits pseudo-random data packets having a first frequency of binary elements, with two double-intervaled binary elements at two predetermined instants t.sub.1 and t.sub.2 for each packet. The receiver has a data regeneration circuit whose threshold varies line by line from a maximum value to a minimum value. The sampling clock of the receiver is at a second frequency lower than the first by the ratio (n-2)/n, where n is equal to the integral ratio of the first frequency to the line frequency of the television. A suitable means insures resynchronization of the sampling clock at the middle of each line.