Where does the energy go?

摘要

In the early 1970s, I worked for Datapoint when it was the leader in distributed data processing. The company manufactured the first desktop computers, and the only reasonable method of program or data entry was a cassette-tape deck. Digital data is much more finicky than music; thus, the tape decks had constant-speed capstan drives, which were more rugged than an audio tape deck. The capstan drive consisted of a brush-less dc motor, four T05 drive transistors, and commutation circuits. Data-point put large numbers of computers with tape decks in the field, and the tape-deck-capstan motor drive had always been a source of field problems; the drive transistors failed sporadically. Because the drive problems came and went, the company lived with the problems.