FORTHRIGHT's Telephone Interface to the PC Watchdog System

The PC Watchdog System provides increased reliability for any ISA bus PC with an available slot, reducing the need for an operator on systems that must stay running. As an auxiliary feature for remote reload capability, FORTHRIGHT has created the Telephone Interface to the PC Watchdog System.

Telephone Interface Philosophy

When we designed the telephone interface, we wanted to design a system that would be safe to attach to your PC. We didn't want a mis-dialed number to accidentally reload your PC. And yet at the same time we wanted a system that was both affordable and simple to use.

The Telephone Interface to the PC Watchdog System is designed to connect your PC Watchdog Board to an inexpensive, external, data (non-fax) modem. From a remote modem you call the modem at the Telephone Interface. When the modems have synchronized, Data Carrier Detect (DCD) is activated. Shortly after DCD is sensed, the Telephone Interface tells the modem to hang up, the end of the "first call". It then starts a timer (which you set in the range of 30 seconds to 2 minutes). If DCD is detected again (a "second call") before the timer expires, the Telephone Interface sends a LOAD command to your PC. If, however, the timer expires first then the Telephone Interface resets internally and waits for a new "first call".

The Telephone Interface to the PC Watchdog System allows you to remotely load your PC with some assurance that it won't be accidentally LOADed by a stray phone call. As discussed above, DCD isn't detected unless called from a data modem. Neither a FAX machine nor a person will simulate this tone. Second, the modem must be called twice in a short interval.


The Telephone Interface retails for $99.95. Variations on the Telephone Interface can be discussed on an as-needed basis. Our engineering costs are moderate and turn-around is typically quick.

For further information or to order, send e-mail to the address below, or call Stan Troeh at (913)299-9240.

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