User`s guide

C-4
ESCALA T610 and PL 600T Users Guide
Ring Detection
Most modems produce an interrupt request each time they detect a ring signal. Some
modems generate an interrupt only on the first ring signal that they receive. AT&T DataPort
2001 is an example of such a modem.
The Service Processor uses the ring interrupt request to count the number of rings when
Ring Indicate Power–On (RIPO) is enabled. If your modem produces an interrupt on only
the first ring, set Ring Indicate Power–On to start on the first ring. Otherwise, you can
choose to start Ring Indicate Power–On on any ring count.
Terminal Emulators
The SP is compatible with simple ASCII terminals, and therefore compatible with most
emulators. It is for the cases when a remote session is handed off from SP to the operating
system that agreeing terminal emulators becomes important.
The servers operating system will have some built–in terminal emulators. Your server may
also have a commercially available terminal emulation. It is important that the local and host
computers select the same or compatible terminal emulators so the key assignments and
responses will match. This will assure successful communications and control.
For best formatting, choose line wrap in your terminal emulator setup.
Recovery Procedures
Line noises, power surges, etc., can sometimes cause your modem to enter an undefined
state. When it is being used for dial in, dial out or Ring Indicate Power–On, your modem is
initialized each time one of these actions is expected. If one of these environmental
conditions occur after your modem has been initialized, it may be necessary to recover your
modem to a known state.
If your modem communicates properly with remote users, it is probably in control. It may be
wise to occasionally change some of the functional settings and then change them back,
just for the sense of security that the modem is communicating, and to assure it has been
initialized recently.
Another strategy, particularly if your system is difficult to access physically, is to protect it
with an Uninterruptable Power Source (UPS) and a phone–line surge protector.
In case recovery becomes necessary, your system should be shut down as gracefully as
possible. Disconnect and reconnect modem power, and power on the system to allow
complete reinitialization of your system.
Transfer of a Modem Session
There are about as many modem command variations as there are modems. The sample
modem configuration files have been written to capture the largest number of workable
modem settings.
The modem command &Dn (where ’n’ is a number) generally sets the modem response to
the Data Terminal Ready (DTR) signal from the servers serial port. The desired response is
that the modem will hold a connection while DTR is enabled, and drop the connection when
DTR is released. This is the mechanism by which the server ”hangs up” on a connection
under normal conditions.
Usually the command &D2 will work, but not always. The sample modem configuration files
take this high percentage position, see the note below. You should consult your modem’s
manual for its specific response scheme for the &Dn command.
There are two methods for dealing with the modem’s response to DTR:
1. Recovery
2. Prevention