2.2.3 Command Line Echo
The modem may echo characters received from the DTE during command state and online
command state back to the DTE, depending on the setting of the E command. If enabled,
characters received from the DTE are echoed in the same format as received. Invalid
characters in the command line or incomplete or improperly-formed command line prefixes
may not be echoed.
2.2.4 Repeating a Command Line
If the prefix "A/" or "a/" is received, the modem immediately executes once again the body of
the preceding command line. No editing is possible, and no termination character is
necessary. A command line may be repeated multiple times in this manner. Responses to the
repeated command line are issued using format of the original command line. If "A/" is
received before any command line has been executed, the preceding command line is
assumed to have been empty (that results in an OK result code).
2.2.5 Types of DTE Commands
There are two types of commands: action commands and parameter commands. Commands of
either type may be included in command lines, in any order.
Action commands may be "executed" (to invoke a particular function of the equipment, which
generally involves more than the simple storage of a value for later use), or "tested" (to
determine whether or not the equipment implements the action command, and, if
sub parameters are associated with the action, the ranges of sub parameter values that are supported).
Parameters may be "set" (to store a value or values for later use), "read" (to determine the
current value or values stored), or "tested" (to determine whether or not the equipment
implements the parameter, and the ranges of values supported).
2.3 Basic Syntax Commands
2.3.1 Basic Syntax Command Format
The format of Basic Syntax commands, except for the D and S commands, is as
follows:<command>[<number>]
where <command> is either a single character, or the "&" character followed by a single
character per V.250. In addition, <command> can be the "%" character followed by a single
character, the "*" character followed by a single character, or the "^" character followed by a
single character.
<number> may be a string of one or more characters from "0" through "9" representing a
decimal integer value. Commands that expect a <number> are noted in the description of the
command. If a command expects <number> and it is missing (<command> is immediately
followed in the command line by another <command> or the termination character), the value
"0" is assumed. If a command does not expect a <number> and a number is present, an
ERROR is generated. All leading "0"s in <number> are ignored by the modem.
2.3.2 S-Parameters
Commands that begin with the letter "S" are known as "S-parameters". The number following
the "S" indicates the "parameter number" being referenced. If the number is not recognized as
a valid parameter number, an ERROR result code is issued.
Immediately following this number, either a "?" or "=" character must appear. "?" is used to
read the current value of the indicated S-parameter; "=" is used to set the S-parameter to a new value
S<parameter_number>?
S<parameter_number>=[<value>]
If the "=" is used, the new value to be stored in the S-parameter is specified in decimal
following the "=". If no value is given (i.e., the end of the command line occurs or the next
command follows immediately), the S-parameter specified may be set to 0, or an ERROR
