Features: HC-05 is a BT2.0 serial port module with mastering-slave integration, which can be switched between mastering and slave with rich and complete instructions (power supply voltages 3.30V-3.6V). Host: used to search for slave devices and cannot be searched by other devices. Slave: The device used to be searched cannot actively search other devices. After the mastering-slave connection, it is equivalent to the use of a serial line. At this time, there is no distinction between mastering and slave, that is, the transparently transmission. This module can be set as a mastering or a slave. The mastering can communicate with the slave but the slave can't communicate with each other or between the mastering and the host. The slave can communicate with computers, mobile phones Specifications: Adopt： CSR mainstream BT2.0 protocol standard Power supply voltages: 3.30V-3.6V Defaulted parameters: rate 9600, pairing code 1234, working slave Size of the module about: 26.8x13x2mm/1.06x0.51x0.08in Working current: pairing: 30~40mA without communication after pairing: 2~8Ma with communication: 8mA without sleep. Communication distance: 10M in opened space and 8Meters in normal use environment. Package Includes: 1PC HC~05 Wireless BT2.0 Transceiver Slave Module note: Due to the problems of lighting effect, there will be certain tolerances in the product, please understand. Please allow 0-1cm error due to the manual measurement.