Craig and Antonelli
Multi-frequency signal receiver
 A multi-frequency signal receiver, in which the digital input signals having the sampling frequency of 8 KHz or a multiple thereof are resampled at a sampling frequency of 4 KHz by means of a resampling circuit and in which the signals thus resampled are subjected to the band selection by means of a digital filter so that the frequency of the input signals may be identified. 
Hitachi, Ltd. Nippon Telegraph and Telephone Public Corporation
H
H04Q
inventional
Eiji Hiroko Akira
Ohira Ito Ichikawa