1、Come with simple operation, most of the serial port commands are single-byte commands 2、Equipped with capacitor filter circuit, improve working stability, very useful and practical 3、The product can be extended by a MO‑94C module to control 4 relays through the serial port 4、Using for STC15F104W as the main control chip, each channel independently set a delay of 1 ~ 255 seconds 5、Onboard 2 relays, relay come with absorption diode circuit, possess excellent performance Item Type: Relay Module Material: PCB Model: SR-10 Interface Description: VCC: Extension module power supply positive GND: Extension module power supply negative P34: CH3 control line, active at high level P35: CH4 control line, active at high level For STC15F104W as the main control chip Each Channel Independently Set: 1 ~ 255 Seconds delay Onboard: 2 Relays(with absorption diode circuit) 1 x Relay Module