MT3334HD8 User Guide
34 CommPlete Communications Server
$MBnModem Baud Rate
n
= speed in bits per second
Default: $MB33600
The $MB command sets a modem’s initial transmission speed for originate mode. In V.32 mode (9600
bps), it also sets the transmission speed for answer mode. With speed conversion on, this t ransmission
speed can be different from the serial port speed.
When the modem answers a call from another modem, it automatically switches it s transmission speed to
match the calling modem. However, if the MT3334HD8 originates a cal l to another modem that is unable
to connect at the transmission speed of the MT3334HD8, the MT3334HD8 will auto matically drop to a
lower speed in an attempt to match the speed of the other modem.
For example, if the MT3334HD8 is set for 14,400 bps and calls another modem that has a top speed of 2400
bps, it will drop to 2400 bps.
$MB75 ITU-T V.23 mode
$MB300 300 bps
$MB1200 1200 bps
$MB2400 2400 bps
$MB4800 4800 bps
$MB7200 7200 bps
$MB9600 9600 bps
$MB12000 12,000 bps
$MB14400 14,400 bps
$MB16800 16,800 bps
$MB19200 19,200 bps
$MB28800 28,800 bps
$MB33600 33,600 bps (factory default)
Speed conversion must be on for this command to work. If baud adjust is on ($BA1), speed conversion is
off and a modem baud rate command will be ignored.
The S48 register also can affect maximum transmission speed. See Chapter 4.
$SBnSerial Port Baud Rate
n
= speed
Default: $SB57600
The $SB command sets the speed of the MT3334HD8’s serial port in both originate and answer modes.
Speed conversion a llows you to s et this seri al port baud r ate at a fixed speed of up to 115,200 bps, regardless
of the modem’s transmission speed setting.
For this command to work, the modem’s baud adjust feature must first be turned off with the $BA0
command. When baud adjust is on, as soon as the modem receives its first AT command, it automatically
adjusts its serial port baud rate to match the speed of the computer or terminal to which it is connected.
However, in applications such as automatic answer, the modem may not receive AT commands. In this
case it is helpful to be able to preset the serial port baud rate with the $SB command.
In addition to setting the modem’s serial port speed, this command sets the speed at which the modem
issues command mode responses (result codes).
The MT3334HD8 accepts AT commands at any speed, regardless of the speed preset by the $SB command.
If the modem receives a command at a speed different from the preset speed, the modem switches its
serial port baud rate to match the new command speed, even though the baud rate value stored by the $SB
command remains the same. This provides you with a convenient way to switch the serial port speed while
still making it easy to automatically return to the original speed the next time the modem is powered up or
reset.