ATC-109 data repeater is a kind of data relay communication product of photoelectric isolated RS-422/RS-485. It can be used with ADC-108 Photoelectric Isolation Interface Converter in combination. TBATC-109 data repeater can prolong the communication distance of RS-422/RS-485 bus network and increase the number of RS-422/RS-485 bus network devices. The inner circuit of TBATC-109 Photoelectric Isolation Data Repeater can detect data direction and switch to control it automatically, conveniently to form a RS-485 network without any shake hand signal. This kind of RS-485 control is fully transparent and need not amend software for the former network basing on RS-422/485 working modes. The built in photoelectric isolator and DC/DC converter can offer 3500V isolation voltage and the rapid Transient Voltage Suppressor (TVS) can effectively inhibit lightning and ESD, provide 1000W lightning strike and surge protection power on each line, and prevent lightning strike and common code interference.