Features:  With isolation gro0ve in control area and load area.  With power and relay action indication, bright when connect and go off when disconnects.  When there is a signal in signal input, public side and common side will breakover.  It can be not only used as a microcontroller development board module, but also as a home appliance control.  It can not only control the DC or AC signal, but the 220V AC load.  With a  permanent open and close vents contact.  It is convenient to connect with blue KF301 terminal access control cable.  Specification:  VCC: Power interface, 5V.  GND: Ground.  IN: Control interface .Drive Current at least 4mA.  COM: Control circuit ground ,Connect to GND.  Size: approx. 41 x 16 x 16mm/ 1.61 x 0.62 x 0.62''.  Weight: approx. 12g.     Note:  1. High level flip-flops shows that there are trigger mode of the voltage between the signal input terminal and the ground; That is to say it is a way of short circuit trigger between signal input and VCC positive pole.  2. Low level flip-flops shows that there are voltage for OV trigger mode  between the signal input terminal and the ground. In a word, it is a way of short circuit trigger between signal input and GND negative pole.  3. Please allow 1-3mm differs due to manual measurement.  4. Due to the different display and different light, the picture may not reflect the actual color of the item. Thanks for your understand.     Package Included:  5 x 1 Channel Relay Module