Canned laughter was one engineer's product, and for about twenty years he had a monopoly on it. Charles Douglass, a CBS sound engineer, built a machine in the 1950s to sweeten single-camera filmed comedies that had no studio audience. His Laff Box held roughly 320 laughs on 32 tape loops, played from a typewriter-style keyboard with a foot pedal to control how long each laugh ran, and included distinct recurring characters such as the person who gets the joke a beat early. He kept it padlocked and operated it himself, and by 1960 nearly every US prime-time show was sweetened by him. Networks did not adopt it out of laziness. In 1965 CBS tested two cuts of a new comedy pilot, one with a laugh track and one without; the laugh-track version tested far better, and the conclusion drawn was that without audience cues viewers could not reliably tell a comedy from a drama. Actors hated it from the start. The convention only weakened in the 1990s, when single-camera comedies without laughter became critically respectable. That is roughly when the split you see in the polling formed.