Having barely recovered from the NVM chip failure debacle I described earlier, lightning struck us again within a year. At the time, the new failure was kept very quiet for reasons that will become obvious, but that was nearly 30 years ago so it’s safe to tell the tale now.
We manufactured a highly secure (for the time) intruder alarm communication system known as Red Care - you may have seen the stickers on high value premises such as jewellers. If an intruder alarm was triggered, Red Care ensured that the Police would be notified. And no, you couldn’t just cut the wires like they show in the films.
The design was stable, with just the occasional small software update. But suddenly we were inundated with returns. All the control boards were failing exactly 45 days after being powered-up. I’m a bit hazy on the details, but my recollection is that a counter overflow was occurring, which led to a coil or transformer being over-driven and burning out.
Again, every product we had shipped was guaranteed to fail very soon and it would take weeks or months to replace them. Burglars would have had a field day if this had become public knowledge.
Again, we concluded that there was no realistic scenario in which we could have found that bug. We used to turn off the equipment at night, so the counter would reset. But even if we left it on, our test window was only about a week so we still wouldn’t have seen the issue.