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Unix Modem Settings

Checking modem settings on SCO Unix

These instructions will help you to determine the communications settings for your Unix attached modem.

screen-shot : Means there is a screenshot available.


1) Log in as 'root' (or any administrative account) to your SCO Unix System.
2) Type in 'more /etc/inittab' and hit 'Enter'. screen-shot

In the 'inittab' file you are looking for the getty settings of your Unix modem. screen-shot
The information will look something like this:

    Se1a:234:respawn:/etc/getty tty1a m

You should have definitions for tty1a(A), and tty2a(A) in that format. You are only concerned with the ones that say 'respawn' as that means they are enabled.

Once you have this information, exit the inittab file.

Note: there may be some other information on the line. You are only concerned with lines that say tty1a, tty1A, tty2a, or tty2A on them.

The letter 'a' immediately after the tty will tell us what communication protocol the Unix modem is setup to use. A lowercase 'a' means that it is using 'software flow control' (Xon/Xoff). A capital letter 'A' means that it is using 'hardware flow control' (RTS/CTS).

In our above example, it shows a lowercase 'a'. Meaning we are using software flow control (Xon/Xoff).


3) Type in 'more /etc/gettydefs' and hit 'Enter'. screen-shot

In the 'gettydefs' file you are going to match up the definition for the inittab information you found.

The letter or number immediately after the tty defines the baud rate for the Unix modem. In our example above, it is the letter 'm'. Looking in our gettydefs file, we see that m is defined as a 9600 baud rate. screen-shot

Using this information

With this information we can now setup our serial program to connect to the Unix modem.

From our above example we would set our PC Serial program to the following settings.

    Communications Protocol/Flow Control : Xon/Xoff (software)
    Baud Rate/Modem Speed : 9600

Note: You can set the baud rate higher then the defined rate on your Unix system. The defined rate is the minimum setting in most cases.

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