In the US, the * key was used for a lot of shortcodes with various add-on phone services -- turning on/off caller id visibility, disabling call waiting for one

In the US, the * key was used for a lot of shortcodes with various add-on phone services -- turning on/off caller id visibility, disabling call waiting for one call, calling the number that dialled you back, etc. However, in general, the keys were designed to be used to access computer services where you needed various delimiters. Of note here is that the DTMF system was originally designed with a fourth row of keys, A-D. These were supposed to be used for general access of menus instead of the now traditional 1-9, but they only ever really got used for the military Autovon [1] network for setting priorities. [1] http://en.wikipedia.org/wiki/Autovon http://en.wikipedia.org/wiki/Autovon