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Gold Medal Software 4
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Gold Medal Software - Volume 4 (Gold Medal) (1994).iso
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SNTLDESC.TXT
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1994-07-20
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What does the Computer Sentinel do?
The COMPUTER SENTINEL is a microcontroller intelligent hardware device that
has a single purpose. It keeps unattended remote access personal computers
available for remote access. The SENTINEL monitors the modem signals and
detects when the modem is no longer available for calls. The SENTINEL operates
automatically and requires no operator intervention to perform its task.
When the SENTINEL determines that the computer is no longer accessible, it
resolves the problem using your pre-configured parameters that are stored in
the SENTINEL during its installation. The goal of these configuration options
is to honor your specific computer system requirements and get the computer
back on-line and available for remote access. This is accomplished by
restarting the computer. When the computer is restarted, your computer batch
files will bring the system back to your desired status.
Many unattended computers perform file maintenance activities (EVENT) at a
pre-determined time. The SENTINEL provides a watch dog timer which monitors
for the event completion. If the EVENT doesn't complete within the specified
amount of time, the SENTINEL restarts the computer to recover from the EVENT
lockup.
System Hardware Requirements
The SENTINEL works with any personal computer system which uses an external
Hayes compatible modem. Just plug it in and forget about it. Menu driven
support utility software is included which operates on IBM PC compatible
computers. This utility is only needed for configuration changes to the
SENTINEL, and the factory defaults serve most system requirements without
modification.
Because the SENTINEL uses no IBM PC computer processing resources, it does not
require any specific computer hardware requirements. Any existing hardware
combinations that support your application without the SENTINEL, will also
operate with the SENTINEL.
The SENTINEL remains outside the associated computer, contained within its own
stand, and has its own power source. The SENTINEL supports all modem
operational baud rates, including the new 38.4K baud and beyond. It has a
front panel status indicator and a front panel control switch. If you order
the optional second port, each port has its own status indicator and control
switch.
The Configuration parameter change utility program communicates to the
SENTINEL with the serial port that is to be monitored. A Sentinel satellite
unit receives the serial port modem cable, and plugs onto the modem data jack.
In other words, the satellite plugs in-between the modem and the serial port
cable of the computer. The satellite unit connects to the SENTINEL with its
own cable, and allows the SENTINEL to monitor the modem status.
If the SENTINEL is used for Bulletin Board System (BBS) monitoring, it can
optionally monitor a second modem port for a total of two modem ports. It can
also interact with other SENTINELS for multi-server Local Area Network (LAN)
BBS systems greater than two modem nodes.
If you are operating multi-node BBS software on one computer, the SENTINEL can
be installed on one port and will detect lockups which affect all ports.
What problems can render your computer inaccessible?
There are basically three things that can go wrong with your computer system
that inhibits remote access capability. One is that the computer itself can
get confused or locked-up. This means that for some reason it is unable to
function properly. Several things can cause this situation. File I/O access
can fail on random occasion, forcing the computer to wait until an operator
performs a RETRY command before continuing. A random memory parity error is
another situation which can cause the computer to become locked-up.
Another situation is when a momentary power failure locks-up the computer's
power supply. This is referred to as a "crowbar" situation which means that
the computer power supply saw a momentary overload (due to the brief power
fluctuation) and shut itself down for self protection. To exit from this
crowbar lock-up, power must first be turned OFF to the computer power supply
and then turned back ON. This same momentary power interruption can also
confuse smart modems and can cause them to lock-up.
The third situation that can render your computer inaccessible, is when the
application software gets confused. This can happen as a result of a burst of
noise coming down the phone line, or can happen due to complex interaction of
software packages. Today, many systems are using multi-tasking software which
adds another dimension of failure possibilities. If your system is connected
to a Local Area Network (LAN), then that environment can also cause your
computer to loose control of the situation.
How does it know when the computer is no longer accessible?
All remote access communications software controls the modem by using modem
commands. The communications software also monitors modem lead states to
determine the modem's status. The SENTINEL monitors modem commands, modem lead
states, and modem responses to determine the status of the entire remote
access system.
When your remote access system becomes inaccessible, it appears from the
caller as one of two possible conditions. Either the line is busy and
therefore inaccessible, or the modem answers but remains dead with no
interaction after the call is connected.
With the SENTINEL satellite unit installed between the computer and its modem,
it has the opportunity of observing the computer, the modem, and the phone
line status. By analyzing the actions of these three entities, the SENTINEL
can readily detect a lock-up while the modem is either on-hook or off-hook,
and take immediate corrective action. This corrective action results in
restarting the computer. When the computer is restarted, your batch files
start up the computer and restore normal operations. This is accomplished by
cycling power to the computer. This is referred to as a POWER CYCLE.
If there is a computer hardware problem, the SENTINEL limits POWER CYCLE
attempts, to prevent further damage to your system.
Installation Configuration Options.
The SENTINEL has been designed for maximum application compatibility and ease
of installation. Listed below are some of the configuration menu options. They
are available for unique applications, but the factory default values are
adequate for most systems.
Power-on Mode Hangup Response Time
Max DTR Cycles Restart Recovery Mode
Type of Port Restart Method
Max Dead Time Pre-Restart Delay
Max Unanswered Rings Restart Duration
Event Timer Duration Post-Restart Pause
Access Solutions Corporation Voice: 609-988-8007
402 Westerly Drive Fax: 609-988-8664
Marlton, NJ 08053 BBS: 609-988-1717