A wireless telecommunications unit is attachable to and detachable from an external unit such as a personal computer, and has a wireless telecommunications apparatus, a microcontroller, and a memory mechanism. The wireless telecommunications apparatus has an identification number for wireless telecommunications, and is for carrying out wireless telecommunications with the outside. The microcontroller is for controlling the wireless telecommunications apparatus and the memory mechanism, it has control functions for the external unit to carry out telecommunications with the outside in accordance with the wireless telecommunications apparatus, to use the memory mechanism as a file system of a designated operating system, when the wireless telecommunications unit is connected to the external unit, and a control function for the wireless telecommunications apparatus to carry out telecommunications using the memory mechanism in accordance with instructions from the external unit or generated in the microcontroller.