It -is- pretty old, dating back at least to the early 1980s. I remember when the series was aired on one of the cable tv channels and I videotaped the segment on vacuum cleaners. Seems to me there were more than three total episodes though.
"Yes", it's old, and "yes", there were more than three parts. In fact there were three series of six parts each. One of the other members posted this link.
The material does seem dated to us now, however when you think of the time they were made, the material would have been quite current, although perhaps somewhat geekishly presented. I still found them informative and entertaining, with a bit of nostalgia thrown in as I lived through that era.