Technical data

Managing Peripheral Devices
8.6 Managing Terminals
See the DECnet-Plus for OpenVMS Applications Installation and Advanced
Configuration for a detailed description of the procedure for setting up dynamic
asynchronous DECnet lines.
8.6.2.2 Determining the Physical Terminal Type of a Virtual Terminal
You can determine the physical terminal type associated with a virtual terminal.
Because both direct connect and LAT lines can be virtual, you might not know the
terminal characteristics of a LAT terminal at system startup time. You can set
the characteristics of direct connect lines at system startup; however, you must
enter a SET TERMINAL/INQUIRE command to determine the characteristics of
a LAT line. (See Section 26.1 for more information about LAT software.)
Note
Using the command SET TERMINAL/INQUIRE clears the type-ahead
buffer.
The following command procedure determines the physical terminal
characteristics of both direct and LAT lines at system startup. Insert the
following lines in your systemwide login procedure (SYLOGIN.COM). (This
procedure assumes that your startup procedure has set all switches and LAT
lines to ‘‘unknown.’’)
$ DEVCLASS = ’F$GETDVI ("SYS$COMMAND","DEVCLASS")’
$ IF DEVCLASS .ne. 66 then goto alldone !Not a terminal
$ DEVTYPE = ’F$GETDVI ("SYS$COMMAND","DEVTYPE")’
$ IF DEVTYPE .ne. 0 then goto got_devtype
$ SET TERMINAL/INQUIRE !Try to determine the device type
$ DEVTYPE = ’F$GETDVI ("SYS$COMMAND","DEVTYPE")’
$ got_devtype:
$! Can now dispatch on ’devtype’ to do different things depending
$! on the type of terminal.
$ alldone:
You can uniquely identify a LAT terminal by using the F$GETDVI lexical function
and specifying the item TT_ACCPORNAM. The function returns the terminal
server node name and port name.
8.7 Managing Modems
A modem is a device that converts electronic signals from one data format to
another. Modems usually perform conversions bidirectionally, that is, they can
convert the local data into another data format and transmit the results; modems
can also receive and convert data back to the local data format. Most modems
convert data from digital format to analog format, and from analog format back
to digital format.
With a pair of modems, you can transmit digital communications over analog
media such as telephone lines, and then convert the communications back into
digital signals at a remote location. Pairs of modems are used to connect a
terminal or a local computer to a remote computer system, and to connect two
remote computers to each other.
The following sections discuss these topics:
• Understanding modems
• Setting up modems
8–24 Managing Peripheral Devices