Features The interface design is humanized, all interfaces can be directly connected through the terminal block, which is very convenient.there are 4 fixing bolt holes for easy installation; The module uses real relays, AC 125V/20A, DC 14V/20A.Fault-tolerant design, even if the control line is broken, the relay will not act; The user can select the control level of the relay, which can be high-level pull-in or low-level pull-in; the module contains a current-limiting resistor, which can be directly controlled by the positive and negative poles of the power supply, or the I /O port control of the MCU control; The working voltage of the module is 5V; there are 1 way, 2 way, 4 way, 8 way, 16 way module to choose from; Using the industry's top quality ultra-small two-way isolation optocoupler, strong anti-interference ability and stable performance,Relay status indicator (red). Module interface: Module input control terminal 1. DC+: External DC power supply positive 2. DC-: External DC power supply negative 3. VREF: Reference ground wire of photoelectric isolation control terminal If high level control is adopted: this signal should be connected to the negative pole of the power supply of the user control board If low level control is used: this signal should be connected to the positive pole of the user control board power supply 4. CH-CH: Relay control interface, If VREF is connected to the negative pole of the power supply: this port is at high level (relative to VREF), the corresponding relay is closed If VREF is connected to the positive pole of the power supply: when this port is at high level (relative to VREF), the corresponding relay is closed Pay attention: the isolated relay module is to adapt to the severe electromagnetic environment or high signal requirements. If you want to achieve a complete isolation effect, the power supply of the user control panel (that is, the reference power supply connected to the VERF) and the power supply of the relay module (DC+/DC-) should be distinguished. If the two power supplies share the same ground, it is not a complete isolation effect. Specification: Size: as shown Voltage: 5V Packing list: 1 x 5V 8-Way 20A Relay Control Module Package List 1 x Receiver 1 x Antenna 1 x Receive Antenna 1 x Data Cable