Widely used. Small size, easy to use. Product Name: 433M 868M Multifunctional Wireless RS485 Bus RF Serial Port UART Transceiver Module DTU for PTZ Camera Modbus RTU Interface: RS485 Working voltage: DC 5V. Working current: 5-40MA. Transmit power: -40-and20dBm Frequency: 433MHz Receive sensitivity: -114dBm Working temperature: -25Celsius-and75Celsius Air-to-ground transmission distance: 500M Dimensions (without antenna): 58.5x30x13.8mm The rate configured in AT mode is fixed as: 9600BPS Transparent transmission mode rate: 1200 2400, 4800, 9600 (default), 19200 How to use ( 2pcs): 1 2PCS, Module 1 and Module 2 send data to each other. 2 3PCS, module 1 sends data, module 2 acts as a repeater (multiple repeaters can be used), and module 3 receives data delay sending and receiving distance. 3 3PCS, one as the master device and the other as the slave device. The way they work as as a wired RS485 bus. The master device sends data, and both slave devices receive data. Any slave device sends data, and the master device and other slave devices can receive it. Previously only one device (master or slave) allowed to send data. Application:PTZ Camera Modbus modbus temperature sensor LED Controller RS485 Relay Remote control, remote measurement system Wireless meter ,Home Automation ,Wiser Home Access control Identification system Data collection IT household appliance Intelligence household appliance Baby monitoring system Colour:green and black Material:PCB board and electronic accessories Package Contents: 2 x RS485 Wireless Transceiver Only the above package content, other are not included. Note: Light and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is 1-3cm.