Bluetooth Universal External Module can be applied to kinds of electronic information products such as family-used equipment and apparatus (medical equipment). As a cable substitute project, it can connect directly with SCM or processor, it adopts plug and play to realize the wireless data transmission between devices. It has two devices used together, a master device and a slave device, which can be used independently or not. It provides safe authentication function, when users set and use it, the connected device must be encrypted, user with encryption can communicate with it, if it is a pair of Bluetooth RS232 module, the process will be completed automatically.