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Modem Functions
Null modem cables can be obtained from most suppliers of computer equipment.
Dial-up modems that operate over normal telephone lines at speeds of 28,800bps or
higher are now available. These modems do not operate at a guaranteed throughput,
but rather at a speed dependent on the quality of the line, the effectiveness of data
compression, and other variables. These modems use hardware flow control to stop the
data from the host by raising and lowering the Clear to Send (CTS) signal.
PortMaster products support hardware flow control using the RTS output signal and the
CTS input signal, which is also used by the normal modem handshake.
Modem Functions
Configure modems to do the following for use with the PortMaster:
•
Raise DCD when a call comes in
•
Reset itself when DTR is dropped
•
Lock the DTE speed
•
Use hardware flow control (RTS/CTS)
Using Automatic Modem Configuration
PortMaster products use a modem table to automate the external modem configuration
process. The modem table is user-configurable and includes long and short modem
names, preferred DTE rate, and the modem initialization string. For convenience, the
table is preconfigured by Lucent for many common modems.
When you specify the name of the modem and the attached port, the PortMaster
automatically configures the modem for you, provided the modem is in the factory
default state when it is initialized.
After a modem type has been specified, the PortMaster automatically sets the port for
hardware flow control, the correct speed, and modem control when the port is reset.
Displaying Modem Settings and Status
To display the external modems currently configured in your modem table, use the
following command:
Command> show table modem
A modem table display looks like the following:
Short Name
--------------
cardinal
mega
supra-288
9-2
Long Name
-------------
Cardinal MVP288XF
Massive MegaFast
Supra V.34
Type
------
System
User
System
PortMaster 4 Configuration Guide
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Troubleshooting
