What is reported in this article is a new application of an old idea. In the 1950s and early 1960s, engineers would check a computer by setting a radio beside the central processing unit to pick up the electromagnetic signals put out by switching vacuum tubes and, later, transistors. By programming so that the switching played a familiar tune, the engineer could detect instantly where bugs were. Some of us from those years can recall standing around a $6 million computer listening to it play “Rudolph the Red-nosed Reindeer” for a Christmas party at Cape Canaveral.

Wayne McCoy
Poolesville, Md.

I worked for Control Data Corp. from 1962 to 1964. I distinctly remember being impressed by a snappy version of a polka that the programmers used to quickly isolate defective cards plugged into the first mainframe computers. This was done by tuning a portable radio near the frame.

John D. Shotzbarger
Minneapolis, Minn.