No photos, please

As new items were added to the menu, we needed to modify existing kitchens to accommodate new equipment. I was tasked with visiting a local unit to confirm some measurements, so before I left HQ, I asked the department secretary if I could borrow the Polaroid camera (this was the 80s) to snap some pictures to help me in this retrofit. Before she could answer me, a voice rang out from one of the nearby cubicles “You can’t take flash pictures in the restaurants!” It was Tony, a long time employee of the R&D department.

“Why not?” I asked.

“Because …” Tony said, “if you use the Flash from the camera in the restaurant, the computer-operated cash registers will shut down!”

Being the new guy, I didn’t want to question his sanity, but I politely responded with, “Huh?”

Tony explained to me that for as long as they had had the new computer registers (3 years), every time a flash was used for the heavily promoted kids’ birthday parties, the stores would need to shut down for at least 15 minutes until the entire system could be rebooted. I went on my assignment (sans camera), but as soon as I returned I began asking questions of everyone, and they all said the same thing. In fact one of the dismrict managers showed me the paragraph in the store operations Manual that forbade flash pictures!

This sounded like an old wives’ tale to me. I discussed it with my boss, and he said, “I’ve just been instructed to lay you off … you were the last hired …”

“But I just started two weeks ago!” I pointed out. “Then solve this flash problem, and we’ll be able to justify keeping you.” With that motivation, I got started.

I had the distribution center send me all the components and cables that a new store would get. This included 2 registers, main computer for the office, 3 monitors that displayed each order, and operator keypads. I set up the entire system in my lab, and was looking forward to proving to management that they didn’t need to tell people they couldn’t take pictures at birthday parties held in the restaurants.

With the system powered up, and sample orders on the screens, I flashed my camera and immediately I heard a loud, eerie, low-pitched sound come from the monitors (each screen also housed a PC board that allowed the individual user to update the orders) and the screens went blank. How could this be? I rebooted the system 10 times, and the same thing happened as long as the flash was within 20 feet of the monitors.

I called the manufacturer, who postulated that the cabling was not shielded properly, causing the flash to affect the signal. They promised to get back to me.

And this was a known problem for three years! Back in my lab, I wrapped the cabling three times around my flash, but covered the light from escaping. Flashing it this time caused no problem. It was the light! But how? I then systematically flashed each component separately until I narrowed it down to the monitors. I took the louvered cover off the back of the monitor so everything was exposed, then I flashed away. It crashed every time. I then narrowed the flash with a foil-covered tube that had a pencil-size opening in the end. I proceeded to expose every square inch to the flash until it crashed.

What did I expose it to that caused this problem? It was a single EPROM (a chip that can be erased by exposing it to UV light). It only had a thin white paper label over the window, The flash was strong enough to disrupt the EPROM’s programming momentarily, causing the whole system to crash. The solution I proposed: black tape over the quarter-inch square window.

That’s all it took. I got to keep my job and parents got to take pictures of their kids’ birthday parties.