Editor’s note: ATM Network technicians have the experience to solve even the thorniest problems, and routinely go above and beyond to do so. This is one such story.

One day the ATM Network service department got a call from a bar and grill in southern Minnesota. Their ATM had suddenly stopped contacting the transaction processor, rendering it useless. When it printed receipts, they said “System unavailable.”

The technician had the owner print out the machine’s electronic journal, which showed that the the ATM was running into “protocol errors”. That usually meant that transactions were getting interrupted in the middle of processing. The most common causes all involve the phone line: too much static, interference from a DSL connection, a shared phone line or (for technical reasons), phone service provided by cable companies.

Further questioning, however, revealed that the bar didn’t have cable TV, much less cable phone service. It didn’t have an Internet connection of any sort, so there wouldn’t be any DSL interference. And the ATM had its own dedicated phone line.

That left static on the line. The tech called the local phone company, which checked its lines and said they were fine. But just in case, they installed a DSL filter to block DSL interference.

A couple of days passed, and the customer called back: the ATM still wasn’t working. In the meantime, the techs had gotten another call from a customer in a neighboring town. He had two machines: One was on an Internet connection, and it was working fine. The other used a phone line, and it was having exactly the same problem as the first customer.

The tech asked which phone company owned the line. It was the same company that served the first customer. This wasn’t unusual: the company serves a large swath of southern Minnesota. The tech called the company and told them a second machine was down. The company checked that line, too: it was fine.

Then a third customer called with the same problem. Different machine, different model – but the same phone company.

The tech thought about it for a little bit, then looked up the phone company’s service area and began calling ATM Network customers in the area. He found four more clients with ATMs that couldn’t communicate with the transaction processor.

He called the phone company for the third time and told them what he found. They still insisted it wasn’t their fault, and suggested it might be ATM Network’s server.

The tech seriously doubted that, but to be sure he called up merchants who had ATMs from competitors that didn’t use our processing network. They, too, reported processing problems.

He called the phone company a fourth time. The company said it couldn’t be their fault, but they’d look into it.

Two days later, everything started working again. The phone company never admitted anything.