This module can be set to a transmitter or receiver transmitter could pairing with receiver receiver and receiver or transmitter and transmitter can't communication between receiver could pairing with computers and cell phone Bluetooth when buying the default for receiver. Note: This module does not suitable for IOS system. CLICK TO CHECK OUT A BLUETOOTH ARDUINO TUTORIAL TECHNICAL DATA LINK FOR HC05 DATASHEET HC05 1. It is HC05. 2. Use the CSR mainstream Bluetooth chip Bluetooth V2.0 protocol standards. 3. Module working voltage 3.3 V. 4. Potter default rate of 9600 the user can be set up. 5. The core module size : 28 mm x 15 mm x 2.35 mm. 6. Working current: matching for 30 MA matching the communication for 8 MA. 7. Dormancy current: no dormancy. 8. Used for GPS navigation system water and electricity gas meter reading system. 9. With computer and Bluetooth adapter PDA seamless connection equipment Commercial Series: Bluetooth module board Series With LED indicator light use 150mA and 3.3V regulation chip. With VCC GND TXD RXD foot for the Bluetooth With Research button(ON/OFF/WAKE foot for it external MCU out/input High level can control module to research) Compatible with Bluetooth master module slave module or masterslave(whole) module. Input voltage: 3.3~6V Size: 1.55 X 3.98 cm Note: input power supply 3.3~6V Prohibit more than 7V No Automatically power supply reversing function so please correctly connect power supply We advise to install Bluetooth master module The State is output foot for LED status when Bluetooth Unconnected output Pulse ; when Bluetooth connected output High level we can determine the states from MCU If only the board No any Bluetooth Function Another COOL Link How to