[in 3,952,425  Apr. 27, 1976
A response analyzer simultaneously receives multifrequency signals transmitted from a plurality of answering devices and forms time divided pulses, which are counted to provide an indication of the number of answering devices which made responses. A plurality of AND gates are each associated with one of the multi-frequency signals, and operate to sample the time divided pulses in order to determine which of the answering devices made responses. Formation of time divided pulses from the simultaneously received multifrequency signals takes place through mixing the respective multi-frequency signals with a local oscillator signal having a frequency which is continuously and periodically varied, to thereby convert the signals into their intermediate frequency versions, from which a fixed frequency component is extracted.
2 Claims, 9 Drawing Figures