The term refers to the global system connected to the mobile network, i.e. a mobile phone or mobile computer connected using a mobile broadband adapter. This is the terminology of 2G systems like GSM. In 3G systems, a mobile station (MS) is now referred to as user equipment (UE).
In GSM, a mobile station consists of four main components:
In a mobile phone, the MT, TA and TE are enclosed in the same case. However, the MT and TE functions are often performed by distinct processors. The application processor serves as a TE, while the baseband processor serves as a MT, communication between both takes place over a bus using AT commands, which serves as a TA.