The original "laugh track" machine, complete with the programming log showing when it was used, was found in a storage unit recently.
Sound engineer Charles Douglass recorded laughter from several sources, such as comedy shows like Red Skelton's, and then set up a machine that would play that laughter or applause at the touch of a key. By using different key combinations, he could avoid -- mostly -- the laughter sounding too repetitive and he could vary the length of the laugh or applause. The Laugh-Track machine is how a show like Gilligan's Island, for example, could have audience laughter even though there was no way that its set could have been built on a sound stage. Same thing with Green Acres or The Beverly Hillbillies.
As is fitting for one of the most annoying inventions ever created, the link leads to a page with an autoplay video, one of the most annoying internet features ever created. It was also written by someone who doesn't know the difference between affective (caused or influenced by the emotions) and effective (having an intended or expected effect), and that make me chuckle a little.