Feature: 1. Functionality: A relay is an electrical control device, which causes the controlled quantity in the electrical output circuit to have a predetermined step change when the change in the input quantity (excitation amount) meets the specified requirement. 2. Interactive System: It has an interactive relationship between the control system (also known as the input circuit) and the controlled system (also known as the output circuit). 3. Automation Ready: Usually used in automated control circuits, it is essentially an automatic switch that uses a small current to control the operating of a large current. Therefore, it plays roles such as automatic adjustment, safety guard, and circuit conversion in the circuit. 4. 8 Bit MCU: The RS232 relay module is designed with a stable 8 bit MCU, complemented by an RS232 level communicating chip, optimizing the performance and reliability of communicating and control systems. 5. 4 Channel Relay Module: Using the standard RTU format of RS232 communicating protocol, it can realize 4 channel input signal detection and 4 channel relay output, which can be used in digital quantity detection or power control occasions. Specification: Item Type: Relay Module Material: PCB Power Supply Voltage: 5-32V Communicating Protocol: Supports Standard for Modbus RTU Protocol Communicating Interface: RS232 Interface Communicating Baud Rate: 4800 9600 19200, Default 9600bps, Supports Power Off Memory Output Signal: Relay Switch Signal Device Address: Range 1-255, Default 255, Supports Power Off Memory Product Size: Approx. 77x64mm / 3.0x2.5in. Package List: 1 x Relay Module