Appendix D; Command Modem Commands - Multitech MMH900 User Manual

Appendix D

Command Modem Commands

Command
A
A/
B
D
Appendix D - Command Modem Commands
Description
Answer
The Answer Mode forces the command modem into
answer mode. Entering ATA when in the Command
mode will immediately bring the command modem
off-hook, out of the command mode and into the On-
Line Answer mode, and cause it to retransmit its
carrier signal over the phone line. If no responding
carrier tone is received within thirty seconds (or
some other time as determined by S-Register S7),
the command modem will cease transmitting its
tone, hang up, and go back into Command mode.
Repeat Last Command
The Repeat Last Command command causes the
command modem to repeat the last command that
was executed. The last command will remain stored
in the modem's command buffer until the Attention
command (AT) is entered. Therefore AT must not be
entered before an A/ command because the A/ will
have no effect if an AT command already cleared the
previous command out of the command buffer.
Bell or CCITT Answer Tone
The B command is used to select the frequency that
the command modem uses for its answer tone. The
answer tone is the tone transmitted by a command
modem receiving a call; this initiates the
handshaking between the two command modems.
At 2400 bps there is no conflict, because all
command modems use CCITT frequencies. At the
lower speeds (0-1200 bps), in the U.S., some
modems use the Bell frequency of 2225 Hz.
However, the CCITT specification for V.22 has an
answer tone frequency of 2100 Hz.
Dial
The letter D in a command will cause the command
modem to dial the telephone number immediately
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