IBM 6H0, Service Manual

Page: 528 / 561

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 service processor is compatible with simple ASCII terminals, and therefore
compatible with most emulators. When a remote session is handed off from the service
processor to the operating system, agreement between terminal emulators becomes
important.
The server’s operating system will have some built-in terminal emulators. You 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 that the key
assignments and responses match, ensuring successful communications and control.
For best formatting, choose line wrap in your terminal emulator setup.
Recovery Procedures
Situations such as line noises and power surges 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 might
be necessary to recover your modem to a known state.
If your modem communicates correctly 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
ensure it has been initialized recently.
If your system is particularly difficult to access physically, another strategy is to protect it
with an Uninterruptible Power Source (UPS) and a phone-line surge protector.
In case recovery becomes necessary, shut down your system using established
procedures. Disconnect the power cable and press the power button to drain
capacitance while power is disconnected. Disconnect and reconnect modem power, and
then reconnect system power to completely reinitialize your system.
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Service Guide