Features 1、4 channel relay output (a normally open, normally closed). 2、4 channel optical coupling isolation. 3、4 relay closed the LED light. 4、Circular DC interface, and DC terminal interface. Convenient power connection (12 v power supply voltage). 5、4 channel input interface. Specification Features: 4 channel relay output (a normally open, normally closed). 4 channel optical coupling isolation. 4 relay closed the LED light. Circular DC interface, and DC terminal interface. Convenient power connection (12 v power supply voltage). 4 channel input interface. A power indicator light. A user LED light. Specifications: LED light: Yes Power supply voltage: 12V Channel: 4 Baud rate: 9600 Microcontroller: STM8S103F3 Communication interface: RS485 Reset button: Yes Size: Approx. 7.8 x 7.7 x 1.8cm / 3 x 3 x 0.7inch Quantity: 1pc Weight: 85g Serial assistant operation instructions: Below are the test instructions for device number 1: No. 1 relay close: 01 06 00 01 01 00 d9 9a No. 1 relay open: 01 06 00 01 01 01 18 5a No. 2 relay close: 01 06 00 01 02 00 d9 6a No. 1 relay open: 01 06 00 01 02 01 18 aa No. 3 relay close: 01 06 00 01 03 00 d8 fa No. 1 relay open: 01 06 00 01 03 01 19 3a No. 4 relay close: 01 06 00 01 04 00 da ca No. 1 relay open: 01 06 00 01 04 01 1b 0a All put out: 01 06 00 01 00 00 d8 0a All light: 01 06 00 01 ff ff d9 ba Reference: Data download address: http://pan.baidu.com/s/1mgzKs3I(The data is in Chinese) Package Included: 1 x 4 Channel Relay Module Note: Please allow 1-3cm differs due to manual measurement. Due to the different display and different light, the picture may not reflect the actual color of the item. Thanks for your understanding. Package List