RS422A differential signal is a kind of bipolar pulse signal formed by level conversion of TTL signal through RS422A differential transmission device.Using shielded twisted pair transmission, the signal level is determined by the voltage difference between the two twisted pairs at the same time. It has the characteristics of long transmission distance and strong anti-interference ability.The time system signal is a standard RS422 differential signal, which plays an important role in the fire control system. The complex programmable logic device CPLD, the high-precision temperature-compensated crystal oscillator, and the standard RS422A differential transceiver device are used as the control device in this article. The control methods for generating, detecting, sending and receiving, adjusting the pulse width and synchronizing the timing signals are elaborated in detail.This method has the characteristics of simple circuit, high reliability, flexible control, high control accuracy, etc. It is widely used in fire control systems.