Module parameters: 1.PCB Size: 37.3mm (Long) *15.5mm (wide) 2. Weight: 3.5g 3. Input voltage: 3.6V--6V, prohibit exceeding 7V 4. Leads 6 feet: EN/VCC/GND/RXD/TXD/STATE (Bluetooth state leads, not connected output low level, the output high level after connection) 5. With the connection status indicator, LED flash indicates no Bluetooth connection; Led slow flash indicates enter at command mode 6. On-board 3.3V voltage regulator chip, input voltage DC 3.6V-6V; When not paired, current about 30mA (due to LED lights flashing, current in the state of change); After the pairing succeeds, the current is about 10mA 7. Effective transmission distance of 10 meters in open area, more than 10 meters is possible, but not to ensure the quality of the connection 8. After pairing succeeds, can be used as full duplex serial port. No need to understand any Bluetooth protocol, but only support 8-bit data bits, 1-bit stop bits, no parity communication format. This is also the most commonly used communication format, does not support other formats! 9. Press the key and then power up the Bluetooth module to enter at mode, set parameters and query information 10. Can switch host and machine mode from at command 11. The module default baud rate is 9600, the default pairing password is 1234, the default name is HC-05Wiring method: VCC: Connect the power supply positive GND: Connecting the cathode RXD: The receiver, the Bluetooth module receives data from other devices, and the sending end TXD of the other devices normally TXD: Send end, Bluetooth module sends data to other equipment; the receiving end RXD of the other equipments normally En: To enable the end, need to enter the at mode when 3.3V Note: this item doesn't works with iOS.Package included: 2 * HC-05 6 Pin Wireless Bluetooth RF Transceiver Module Serial BT Module for Arduino