The Adventure of the Camera-Shy Computer

Marc Mann, Contributing Writer

In the mid ’80s I provided technical support to the R&D division of a large fast food chain. I tested new appliances and just about anything else that went into the stores to ensure reliability and overall compatibility. While planning to install a new appliance for testing, I found we didn’t have a blueprint of the test location. I asked one of the architects if the department had a camera so I could take some pictures of the installation. Tony replied “You CAN’T Take Flash Pictures in the Store!” When I asked why he said, “Because the computer cash registers will shut down!”

By the tone of his voice, I knew he wasn’t kidding me, but his answer made no sense. I asked several other employees, and one even told me to consult the operations manual. In the section pertaining to the “Operation of the Computer Cash register and Order Taking System”, a prominent warning was displayed: “Do Not Allow ANY Flash Pictures in the Register & Kitchen Area. Doing so will cause the system to fail and will require a minimum of 15 minutes to re-set & re-boot.” In other words, the store would effectively be put out of business until the system was back up and running.

I approached our department director and asked permission to investigate, and he agreed. Before going further, I called the computer manufacturer and was told that they had heard reports of this happening only sporadically. They theorized that the high voltage coil of the camera’s flash was being picked up by the cabling, which was acting as an antenna. Their solution: “Don’t use a Camera Flash in the Stores.”

With that information, I ordered a complete register system, consisting of 3 registers, 4 kitchen/drive thru monitors with keypads, office computer, and interconnecting cables. I set these up in my lab and booted things up. I brought in a stand-alone camera flash from home and skeptically fired off a shot.

Immediately all the monitors sounded a deep screeching noise (each monitor had a keypad & tone alert to delete completed orders), and the CRT went blank except for a thin white vertical line. Everything was unusable. I rebooted the system and it did the same thing. I then covered the strobe’s window and fired. The system didn’t fail! I then wrapped three feet of cabling around the strobe. Again, it didn’t fail. It was the light! But how? I then physically isolated each device and “lit it up.”

Everything worked until I got to the monitors. These monitors had a louvered housing and were ceiling mounted. When flashed from any angle the system failed. I then disassembled a monitor and found a separate internal motherboard that communicated with the operator’s order keypad and registers.

I then placed the flash in a cardboard tube and drilled a single quarter-inch hole to limit the flash to a tiny area. I flashed every inch until I got to one component and voila! It was an EPROM (Erasable Programmable Read Only Memory). Its quartz window was covered by a white adhesive label with its date of programming. It should have been a light-tight foil label. Evidently one of the wavelengths of the flash contained sufficient UV Light (normally used to erase EPROM’s) that disrupted its operation. Subsequent research found those paper labels lying inside the cabinets. The adhesive failed due to the heat of the kitchen, increasing its susceptibility to “Flash” failure. The fix was to apply foil labels.

Simple as that.

Marc R. Mann lives in San Diego and is a 30-year veteran of the Commercial Food Equipment Field. He has held positions in R&D, Service, and Operations and is currently a consultant.