72377667
Dec 2, 1970
Apr 4, 1972
MODULATING AND DEMODULATING EQUIPMENT FOR MODULATING AND DEMODULATING A CARRIER FREQUENCY WAVE FORM SO THAT IN A COMPLETE TELEPHONE CIRCUIT ONE SUBSCRIBER MAY TRANSMIT AND RECEIVE SIGNALS AT ONE FREQUENCY LEVEL AND ANOTHER SUBSCRIBER MAY SEND AND RECEIVE SIGNALS AT A DIFFERENT FREQUENCY LEVEL
Housewares and Glass