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