Frequency shift keying apparatus Patent

Frequency shift keying apparatus for use with pulse code modulation data transmission syste

Frequency-shift-keyer circuit improves PCM conversion for radio transmission

A data logic circuit employing a fixed frequency, square-wave oscillator and flip-flop gates allows for the shifting from one frequency to the other at the end of a whole number of cycles of one shift frequency and at the beginning of a cycle of the second shift frequency