PROBLEM TO BE SOLVED: To provide a communication system, a transmitter and a receiver, capable of performing stable signal transmission with a simple configuration.SOLUTION: An endoscope system 1 includes: a reference clock signal generator unit 407 for generating a clock signal a synchronous signal generator unit 408 for generating a synchronous signal on the basis of the clock signal a modulation unit 409 for modulating either one of the clock signal and the synchronous signal to generate a modulating signal, and transmitting the modulation signal and the other signal through a transmission cable and an extraction unit 247 for receiving either the clock signal or the synchronous signal, and the modulation signal, through a transmission cable, and extracting, from the modulating signal, a signal which is necessary for operation.
