It was rarely shown, but there was actually a television set in the apartment, located on the lower left corner of the audience's view. As I recall, there were two incidents in which the characters were watching television. Both are in the often omitted tag scenes:

Eyewitness Blues #0605
The characters are watching a TV news broadcast about the incident with the robber and detective in the apartment.

Star Struck #0716
Janet shows Terri that Bret Wade's character is killed on his soap opera.

Were there other episodes in which the TV set was used?

Wasn't there an episode where Jack was watching a Lakers game? Also, I seem to remember Furley and someone else playine some type of video game on it. I don't know if you could actually see it, but it was there.

yes, but it was jack and janet (or chrissy) who were playing and mr furley came into the appartment

There was also the episode where the FBI wanted Jack. In the beginning Janet says she was going to stay home and watch a good movie on t.v. Jack and Janet were playing a video game when Mr. Furley walked in on another episode.

In the epid. Ground Rules, when it was Janets turn to stay @ home, and Chrissy wanted the apt. that night, Janet tells her that she was in luck, b/c the TV wasn't working, like the volume was out or something!