Description: With 4 fixed screw holes, convenient installation and fixation. Widely used for all MCU control, industrial sector, PLC control, smart home control. Interface design user-friendly, all interfaces are available through Terminal direct connection leads, very convenient. 1/2/4/8/16 with optocoupler stype: The use of the industry's top quality optocoupler isolation, strong anti-interference ability, stable performance. 16 channel: Each relay common COM are for independent, user-friendly access to different signals, each relay are normally closed and normally open with a port. Specifications: Materials: Metal, Plastic, Electric Parts. Color: show as pictures. 1 CH Without/With Optocoupler(Black): Pole Number: 1 Channel. Load: 10A, AC 250V, DC 30V. Overall Size: 4.7 x 2.8 x 1.7cm. 1 CH Without Optocoupler(Blue): Size: 53mm*28.3mm*19.3mm. Equiped with high-current relay, AC250V 10A ; DC30V 10A. 5V 1-Channel Relay interface board, and each one needs 15-20mA Driver Current. Indication LEDs for Relay output status. It can be controlled directly by Microcontroller (for Arduino , 8051, AVR, PIC, for DSP, ARM, ARM, MSP430, TTL for logic). 2 CH With Optocoupler(Black): Size: 50.5*38.5*18.5cm. Equiped with high-current relay, AC250V 10A ; DC30V 10A. 5V 2-Channel Relay interface board, and each one needs 15-20mA Driver Current. It can be controlled directly by Microcontroller (for Arduino , 8051, AVR, PIC, for DSP, ARM, ARM, MSP430, TTL for logic). 4 CH With Optocoupler(Blue): It can be controlled directly by for Micro-controller (for Arduino , 8051, AVR, PIC, for DSP, ARM, ARM, MSP430, TTL for logic) . 5V 4-Channel Relay interface board, and each one needs 50-60mA Driver Current. Equiped with high-current relay, AC250V 10A ; DC30V 10A. Size:7*5.3cm Indication LED’s for Relay output status. 8 CH With Optocoupler(Blue): Size: 13.5 x 5.3 x 1.7cm (LxWxH) Working voltage: 5V. Channel: 8 channel. This relay module is 5V active low. It is an 8-channel relay interface board, which can be controlled directly by a wide range of microcontrollers such as Arduino, AVR, PIC, ARM, PLC, etc. Relay output maximum contact is AC250V 10A and DC30V 10A. 8 CH Without Optocoupler(Black): Easy to use, simple 3 line structure. Power LED(Green), 8 relay status indicator LED(Red). Output Channel: 8. Working Voltage: DC 5V. Relay Load Voltage: AC 125V/250V 10A; DC 28V/30V 10A. Size: 4.4cm x 13.8cm. 16 CH With Optocoupler(Blue): 1-16 road can be any for full on / off, or any road. Output Type: AC 220V 10A directly connected or DC30V 10A load. CB board size: 180MM (L) * 90MM (W) * 20MM (H). Package include: 1 * Relay Board Module.