Control of Frequency Synthesizer of NMR Through PC Computer

In order to control PTS frequency synthesizers by PC computer,designed a simple circuit.By using this circuit and through the parallel port of PC computer,the main program written in C language can easily control output frequency of PTS frequency synthesizers.The menu operation method is used in the main controlling program and the +5V power of the circuit is supplied by the PC computer.The use of this system is very easy and it is worth to extend the application of this system.