                         Revision date: 25 Oct 92
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ͻ
     This tutorial describes Computer Sentinel which monitors an             
     unattended remote access computer modem and provides automatic          
     recovery if the computer becomes locked up.                             
                                                                             
     The SENTINEL was designed for easy installation and set up. It works    
     in an office environment or with a BBS system. A second modem and/or    
     computer can be monitored with the second port option.                  
Ķ
             This tutorial consists of the following topics:                 
                                                                             
    1. This screen you are now reading    7. Sentinel Functional diagram     
    2. What does the Sentinel do?         8. Sentinel Single Modem diagram   
    3. Wide area BETA Test Program        9. Sentinel Multitasking diagram   
    4. Condensed Installing Instructions 10. Sentinel LAN Network diagram    
    5. Condensed Operating Instructions  11. Sentinel Daisy Chain diagram    
    6. How to order the Sentinel         12. Sentinel Power Cycle diagram    
                                                                             
           This information can be downloaded as SNTLLIT9.ZIP                
ͼ


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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 in
one of two possible ways.

The first approach, is to simulate pressing the computer RESET switch if one
exists.  This is done electrically by the SENTINEL instead of mechanically as
an operator would do. If your computer does not have a RESET switch, then the
other method of restarting the computer is to turn OFF power to the computer
for a specified number of seconds, and then turn the power back ON.

This is referred to as a POWER CYCLE. This will cause the computer to forget
its past problems and start up fresh and new. The SENTINEL can also use a
combination of these two methods. It can use the RESET approach first, and if
that fails, resort to the POWER CYCLE approach. If both of these approaches
fail, then there is a computer hardware problem and the SENTINEL limits POWER
CYCLE attempts, to prevent further damage to your system.


   How is power cycled to the computer/modem by the COMPUTER SENTINEL?

The SENTINEL uses optional Plug-n-Power modules which are sold at your local
Radio Shack store. These modules are U/L approved and allow the SENTINEL to
cycle power to the computer and/or the modem, when necessary. The SENTINEL
connects directly to the Plug-n-Power Universal Interface Control Module,
which is Radio Shack part number 61-2687. This module, in turn, controls other
Universal Appliance Power Modules, which are Radio Shack part number 61-2684.
You would plug your computer and/or modem into the Universal Appliance Power
Module.

                      Operational Status Indicators.

The SENTINEL has a front panel LED status indicator and a control switch.
Together, they provide continuous indication of what the SENTINEL is doing.
Although these front panel functions are not used for unattended operation,
they are handy for system installation, maintenance, and monitoring. The
control switch can change the active/disabled state of the SENTINEL, and can
also display the number of previous restarts that may have occurred. This
permits manual control while the modem is in use, and provides status of your
system. Below is a list of the available status displays:

        1. "Test" mode, status indications only, no restarts
        2. "Active" and monitoring the system operation
        3. "Disabled" and not monitoring the system
        4. "Recovery" mode, caller just now disconnected
        5. "Pending" warning, restart is about to take place
        6. "Restart" mode, currently restarting the computer
        7. "Command" mode, awaiting configuration changes
        8. "Connected", caller's modem carrier is present
        9. "Event" mode, event watchdog timer is active
       10. "Save" mode, updating the non-volatile configuration


                 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


We currently offer a limited time, SYSOP special pricing Program, with
substantial price reduction. For additional information, call:

                     ACCESS SOLUTIONS CORPORATION
                             18 Ivy Lane
                       Cherry Hill, NJ 08002
                609-667-7628 Voice   609-667-5652 BBS



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       COMPUTER SENTINEL Wide Area BETA Test Program     25 Jun 92

  The Wide Area BETA program was completed successfully and has been
  discontinued.


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Computer Sentinel Condensed Installation Instructions    23 May 91

1. Unplug the computer serial port cable from its associated
modem. Plug the Sentinel Satellite unit onto the modem and then
plug the serial cable onto the Sentinel Satellite unit.

2. Plug the Sentinel Satellite ribbon cable into jack J1 of the
Computer Sentinel. This J1 is located at the rear of the Computer
Sentintel and is clearly labled.

3. If you have the second port option, repeat steps 1 and 2 using
J2 of the Computer Sentinel and the second Sentinel Satellite
unit.

4. Plug the provided Power-Pack cable into P1 on the rear of the
Computer Sentinel. Now plug the Power-Pack into a house current
wall outlet.

5. At this time the Computer Sentinel should display an "A" or
"c" on the Port-A display. The "c" means that the serial port DTR
lead is low and the modem is not in use. This is called the
command mode, because modems are never used when DTR is low.
Therefore, if DTR is low, the Sentinel reads the serial port
looking for commands. When DTR is high, the Sentinel ignores the
serial port data in case modem data looks like a Sentinel
command. When you start to use that modem, the "c" will change to
an "A" which means that the Sentinel is activated and monitoring
the port.

6. Now you must interface the Computer Sentinel to the computer
to cause it to restart when it gets locked up. One way to do this
is to install the reset cable from the computer to the Computer
Sentinel, J3. This will enable the Sentinel to electrically press
the computer reset switch when a lockup occurs. The instructions
for installing this cable are given in the user's manual.

If you don't wish to install the reset cable, or if your computer
doesn't have a reset switch, you can purchase and use Radio Shack
Plug-n-Power modules. These modules will allow the Sentinel to
remove power from the computer, and then reapply power effecting
a restart. The instructions for installing these optional power
modules are given in the user's manual.

7. This completes the hardware installation of the Sentinel
device. The default Sentinel parameters are sufficient for most
systems, but if you wish to modify these parameters, use
SNTLCFG.EXE which is a utility for changing the desired
parameters within the Sentinel.


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      COMPUTER SENTINEL Condensed Operating Instructions  09 Oct 91

1. Only Port-A of the SENTINEL will recognize commands from the computer.
Port-B can only monitor a modem's status.

2. To activate the SENTINEL, use the file SNTL.EXE [ON] which will cause the
display to show "A" which means the SENTINEL is now activated and is
monitoring the system. You can also use the front panel control switch to
toggle the SENTINEL active.

3. To disable the SENTINEL, use the file SNTL.EXE [OFF] which will cause the
display to show "d" which means the SENTINEL is now disabled. You can also use
the front panel control switch to toggle the SENTINEL Disabled.

4. To RESET the SENTINEL, use the file SNTL.EXE [RESET]. This is the same as
powering up the SENTINEL for the first time.

5. To start the EVENT TIMER function, use the file SNTL.EXE [EVENTON]. When
this utility is executed, the display blinking dot will go OFF and remain off
until SNTL.EXE [EVENTOFF] is executed which cancels the EVENT TIMER. Any
action which changes the SENTINEL state from active to disabled, or vice-
versa, will also cancel the EVENT TIMER. Any restart performed by the SENTINEL
will also cancel the EVENT TIMER.

6. To place the SENTINEL in TEST mode, use the file SNTL.EXE [TEST]. While in
the test mode, the display blinking dot will remain steady ON. While in the
test mode, the display status will work but the computer(s) will not be
restarted. If you have two or more SENTINELS daisy chained together, remember
to place all sentinels in TEST mode. To exit this test mode, momentarily press
the front panel control switch, or use SNTL.EXE [RESET].

7. The display indications have the following meaning; "A"=Activated,
"d"=disabled, "r"=recovery mode, "0-9"=counts remaining until restart,
"H"=hard restart in progress, "P"=pause after restart, "S"=save new config,
"="=successful command, "F"=unsuccessful command, "b"=faulty new cfg data,
"n"=carrier connect, "c"=command mode (DTR low), blinking dot=normal
operation, constant dot=test mode, no dot=event timer activated.

8. The SENTINEL is delivered with the following default parameters. Use
SNTLCFG.EXE to modify for unique applications:

HANGUP RESPONSE TIME - Number of seconds allowed for this port to recover from
caller hang-up. If no response within this time, force a restart. Default =
240. [10-255]

MAX DEAD TIME - Maximum number of seconds since the system last had a valid
caller. If this time elapses, a forced restart will result. 65000 disables,
Default = 65000. [0000-65000]

PRE-RESTART DELAY - Once a forced restart is scheduled for this port, this is
the number of seconds delay before conducting the restart. Default = 10. [1-
255]

RESTART DURATION - How many seconds the forced restart will last. During this
time the computer is held reset and/or the power remains off. Default = 4. [2-
255]

POST-RESTART PAUSE - After the restart duration has expired, this is the
number of seconds delay before the Sentinel begins monitoring again. Default =
60. [10-65000]

MAX UNANSWERED RINGS - This is the maximum number of un-answered rings since
last valid caller, before the Sentinel forces a restart. Default = 12. [4-255]
Setting this parameter to 255 disables the ring count feature.

MAX DTR CYCLES - This is the maximum number of times since last valid caller,
your software can attempt to command your modem on-hook before a restart is
forced. Default = 24. [4-255] Setting this parameter to 255 disables this
feature.

EVENT TIMER DURATION - Maximum number of seconds before the event watchdog
timer expires and forces a restart to recover from an event lock-up condition.
Default = 10800. [256-65000]

POWER-ON MODE - After a temporary power interruption, this determines whether
the Sentinel will wake up ACTIVE or DISABLED. Default = ACTIVE.

RESTART RECOVERY MODE - After the Sentinel completes a restart, this
determines if it remains ACTIVE or goes to a DISABLED state. Default = ACTIVE.

RESTART METHOD - RESET = force reset only. POWER = force power cycle only.
BOTH = RESET & POWER together.
SEQ = first do RESET then if that fails, do POWER. Default = BOTH.

TYPE OF PORT - Defines which ports will force restarts when this port
restarts. MASTER means force other ports and other Sentinels. SLAVE forces
this port only. PADS means this port is used with X.25 PADs, and is not
used with a modem. PADS do not force restarts to other ports or Sentinels.
Default = MASTER

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              How To Order a COMPUTER SENTINEL  25 Oct 92


To order your Computer Sentinel, call voice 609-667-7628. If you call
outside normal working hours (EST) you can leave your phone number and
we will get back to you. You can also fax your order by calling
609-482-8482. Be sure to include your purchase order number, specify if
you want the optional second port, and specify if you need 5-1/4 or
3-1/2 support utilities diskettes. We currently accept check, money
order, and COD as forms of payment.



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                    Computer Sentinel Functional Diagram

   Port A    Ŀ Ŀ
 Serial cable Sentinel    Port               External reset command from
 Ĵ Satellite Ĵ  A                  other Sentinel units, which
              Unit-A     Modem                will cause this Sentinel to
                             restart its computers.
                                               
                          Port-A computer           External reset command
 One Satellite            restart control.           to force other Sentinel
 module included          Connects with              units to restart their
 with each Sentinel.      computer reset             associated computers.
 Two included with        switch and/or            
 2nd port option.         power control                  To external
                          module.                            9VDC power
                           Ŀ pack unit.
                                            J4   J5    P1   
                                 Ĵ   J3         J6   Ŀ
                       Ĵ   J1         J2    Optional
 Port-A Status display indicator - DSPLYA     DSPLYB -  Port-B
 Port-A Control Switch -  SWA        SWB   -
                                            Computer Sentinel 
                                           



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                Computer Sentinel Single Modem Installation

   Ŀ  Ŀ  Port A
    Port    Sentinel  Serial cable       Ŀ
     A   Ĵ Satellite Ĵ Serial Port #1          
   Modem    Unit-A                                                
                               COMPUTER-A        
                                                                     
                                 Ĵ Reset switch connection 
 Refer to Sentinel                         
 power cycle diagram             
 for example of power            
 control use of the              
 Sentinel.                                                To external
                                                              9VDC power
                                         Ŀ pack unit.
                                                       P1   
                                 Ĵ   J3              
                       Ĵ   J1              
 Port-A Status display indicator - DSPLYA            
 Port-A Control Switch -  SWA              
                                            Computer Sentinel 
                                           


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                  Computer Sentinel Multitasking Installation

Ŀ  Ŀ
 Port    Sentinel    Ŀ  Ŀ  Ŀ
  A   Ĵ Satellite Ĵ Serial Port #1             Sentinel     Port 
Modem    Unit-A                Serial Port #2 Ĵ Satellite Ĵ  B   
                                Unit-B      Modem 
                                Computer             
                                                             
 * Configure the      Ĵ Reset switch connection             
   Sentinel device                 
   for two server                                             
   node types, and                        To external    
   J3 will restart                            9VDC power     
   the computer          Ŀ pack unit.     
   for both ports.                     P1                   
                      Ĵ   J3         J6    Not used *   
                    Ĵ   J1         J2   
 Port-A status indicator - DSPLYA     DSPLYB - Port-B status indicator
 Port-A control switch -  SWA        SWB   - Port-B control switch
                            Computer Sentinel 
                           




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                  Computer Sentinel LAN Network Installation

Ŀ  Ŀ
 Port    Sentinel    Ŀ           Ŀ  Ŀ
  A   Ĵ Satellite Ĵ Serial Port #1             Sentinel     Port 
Modem    Unit-A       * Computer-A           Ĵ Satellite Ĵ  B   
   ڴ Reset switch              Unit-B      Modem 
                                   
                       Ŀ                    
 * Configure the        Serial Port #1             
   Sentinel device      * Computer-B                        
   for required           Reset switch Ŀ  
   node types, if       To external   
   one of these                               9VDC power    
   computers is a        Ŀ pack unit.    
   slave node.                         P1                  
                       Ĵ   J3         J6     
                    Ĵ   J1         J2   
 Port-A status indicator - DSPLYA     DSPLYB - Port-B status indicator
 Port-A control switch -  SWA        SWB   - Port-B control switch
                            Computer Sentinel 
                           



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                   Computer Sentinel Daisy Chain Installation

     Unit-I has one or more LAN server nodes.
     Unit-II has no LAN server computers, only slave nodes.
     If Unit I restarts, Unit II and its associated node(s) will restart.
     #1-#2 are included cables required for daisy chaining this system.
     All cable connections are optically coupled for electrical isolation.

                  #1Ŀ
                  #2                   
                                        
                                        
              Ŀ    Ŀ
                 J4   J5    P1          J4   J5    P1   
                 J3        J6           J3        J6    
                 J1        J2           J1        J2    
               DSPLYA    DSPLYB       DSPLYA    DSPLYB  
                SWA       SWB          SWA       SWB    
               Computer Sentinel      Computer Sentinel 
                  
                      Unit-I                  Unit-II



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                   Computer Sentinel Power Cycle Diagram

   Ŀ  Ŀ   Ŀ   Ŀ
    Port    Sentinel   Ĵ Serial Port #1    110VACĴRadio Shack     
     A   Ĵ Satellite                              Appliance module
   Modem    Unit-A              COMPUTER-A           # 61-2684       
                                    
                          Ĵ Reset switch connection             
                                       
 Note that J3 can have    #1     Ŀ      Ŀ
 two cables connected           Radio Shack          110VAC House 
 to it. #1 goes to        #2ĴPlug-n-power  Ĵ wall outlets Ŀ
 the computer reset            control module        
 switch. And #2 goes           #61-2687               Ŀ       
 to the Plug-n-power                                 
 control module. The                    Ŀ Ŀ
 optional Radio Shack     Ŀ                P1    External  
 modules are UL apprvd    Ĵ   J3               9VDC power
                       Ĵ   J1               pack unit 
 Port-A Status display indicator - DSPLYA             included  
 Port-A Control Switch -  SWA               with each 
                                            Computer Sentinel  Sentinel  
 All Sentinel jacks are optically coupled.  


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