Meanwhile, a Sprint engineer was trying to make sense of the number that GTE had traced as originating from the Sprint network. When he searched through the company’s customer records, the number didn’t come up, which seemed strange. But then the engineer realized it wasn’t a Sprint number at all—in fact, it didn’t even have a cellular prefix. Shimmy asked the FBI to set up a conference call so he could discuss this oddity with the engineer at Sprint. Then he decided to try calling the number himself, to see if anyone would answer. As soon as the call connected, he began to hear a kerchunk- ing noise that would get quieter and quieter until the call was dropped. This was intriguing to him and the engineers. It appeared that I had set up a fail-safe to prevent them from tracing me back, and they wondered if I could have tampered with the switch.