The ATD command sets a voice, data or fax call.
ATD<str>;
Dial the dialing string <str> with the voice utility
Valid dial modifiers: ”T” (tone dialing), ”P” (pulse dialing) is ignored.
The character ”;” is important, for this tells the phone that the call
should be set up with the voice utility. Otherwise an attempt is made to
set up a data call, which the phone immediately acknowledges with
”ERROR”.
The dial command responds with OK to the user right after starting a
voide call.