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2.2.2 Call Control commands and response
2.2.2.1 Dial (D)
Table: Syntax (D)
Command
Possible response(s)
D[<dial_string>][;]
Description
This command instructs the DCE to originate a call. This may include several
steps, depending upon the DCE type, such as: connecting to the line (going
off-hook), waiting for the network to indicate readiness to receive call
addressing information (wait for dial tone), signaling call addressing
information to the network (dialling the number), monitoring the line for call
progress signals (e.g. busy), and instructing the underlying DCE to start the
call origination procedure (modulation handshaking).
All characters appearing on the same command line after the "D" are
considered part of the call addressing information to be signaled to the network,
or modifiers used to control the signaling process (collectively known as a "dial
string"), up to a semicolon character (IA5 3/11) or the end of the command line.
If the dial string is terminated by a semicolon, the DCE does not start the call
origination procedure as defined for the underlying DCE, but instead returns to
command state after completion of the signaling of call addressing information
to the network.
Any characters appearing in the dial string that the DCE does not recognize as
a valid part of the call addressing information or as a valid modifier shall be
ignored. This permits characters such as parentheses and hyphens to be
included that are typically used in formatting of telephone numbers.
Abortability
The D command may be aborted in the manner described in 5.6.1. If the DCE
is connected to the line, it disconnects from the line in an orderly manner as
required by the state of the connection. Aborting the connection by reception of
a character is generally possible at any time before the DCE enters online data
state, but may not be possible during some states of connection establishment
such as handshaking. The DCE shall issue a final result code; which result
code to issue shall be determined by the manufacturer, and may depend upon
the state of the connection at the time the character was received from the