Broadcast on network TV in the United States to fill a 200 minutes time slot; later cut to 150 minutes [...]
DVD contains 183 minute version which is the complete mini-series.
Salem's Lot originally aired on CBS on November 17th and 24th of 1979 in two 2-hour segments. The following year, CBS aired an edited version of the miniseries in one 3-hour segment.
So I guess the two 2-hour segments was the 90-minute parts plus advertisements and the 3-hour version was 150 minutes plus 30 minutes worth of ads.
Also, there was a 112 minute cut that was released theatrically in Europe in various versions. It had some alternate scenes, most of which are contained in the now official DVD version. It apparently also had different music in parts.
Q: Salem's Lot (1979) was also done for television with a shorter version released in Europe as a feature. Tell me something about making it.
A: I had met James Mason before at the Cannes Film Festival. He is one of our best actors, highly regarded in Europe, a joy to work with. The director, Tobe Hooper, had asked for me from the start. The makeup and contact lenses were painful but I got used to them. I liked the money best of all. The scene where David Soul stakes me took many retakes because Tobe wanted me to die in a certain way. I never saw the other version but the cuts wouldn't have affected me anyway.