One of the most important and remarkable discoveries was electricity. The practical use of electricity has only been at our disposal since the mid-to late 1800s . The first method of generating electricity was by creating a static charge. In 1660 Otto von Guericke constructed the first electrical machine that consisted of a large sulphur globe which, when rubbed and turned, attracted feathers and small pieces of paper. Guericke was able to prove that the sparks generated were truly electrical.
AT commands are a group of commands that can be sent by a terminal or host computer to control the ISU (Iridium Subscriber Unit ) in Command mode.
When the ISU is in command mode (or off-line mode), AT commands can be entered to control the phone.
When in data (also called on-line) mode, the ISU is connected to a remote system and any characters sent it will be transmitted to the remote system. It is possible to enter the command mode without terminating call by using the +++ escape sequence detailed below.