1. Long-distance wireless transmission (up to 500 in open area , 10kbps rate in the air ).2. Operating frequency range ( 433 - 458.5MHz , up to 255 communication channels). Maximum 100mW ( 20dBm ) transmit power ( 10 levels of power can be set ).3. Built-in MCU, use serial port to communicate with external devices. Send 31 bytes at a time.4. The module can support one-to-one, one-to-many transparent transmission communication through ID setting Changing the rate of a different serial port will synchronously change the rate at which data is sent over the air. ( 10kbps-100kbps)5. Set the 'critical three minutes'. The module can send and receive data normally within three minutes of power-on. You can send the AT ' AT+ENABLE=1 ' to make the module enter the AT state for parameter setting. There is only this reserved word in these three minutes. After more than three minutes, you will not be to enter the AT mode, you can only send and receive data, ' AT+ENABLE=1' will also be sent out as data, there are no reserved words at this time.Product Name: VHF/UHF Radio Modem RS485 Wireless Transceiver 20DBM 433mhz Transmitter and ReceiverWorking voltage: 4.5V-5.5V;Interface : RS485(5V GND A+ B-)Frequency: 433MHzTransmit power: -40~+20dBm;Receiver sensitivity: -114dBm;Operating temperature: -25 Celsius~+75 Celsius;Transparent transmission mode rate :1200 2400,4800,9600(Default),19200;Open ground Transmission distance : 500MSize(without antenna): 74 x 24 x 16mmRecommend to than 2pcs!!!How to use (more than the =2pcs):1/2PCS,Module 1 and Module 2 send data to each other.2 more than the =3PCS,One as master device, the other as will be as slave device.the way they work as as wired RS485 bus. Masterdevice transmit data, Slave devices all receive data.Any slave device transmit data, master device and the other slave devices can receive .When ever only allowed one device (master or slave) to transmit data.Application:IP PTZ CameraModbus modbus temperature sensorLED ControllerR4D3C32 N4D8B08 N4D8C12 RS485 RelayRemote control, remote measurement system;Wireless meter ;,Home Automation ,Wiser Home;Access control ;Smart meterColour:blueMaterial:Plastic + MetalPackage Contents:2 * 433M-458M VHF/UHF Radio Modem RS485 transceiver(With shell)Only the above package content, other products 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.