A frequency shift keying system for transmitting a signal which is a function of supplied data, includes first and second frequency generators producing first and second frequencies which differ in value by an amount which is a function of the maximum baud rate of the data. A counter is responsive alternately...http://www.google.com/patents/US5014285?utm_source=gb-gplus-sharePatent US5014285 - Frequency shift keying communication system with selectable carrier frequencies
