[Jeffhs]

In the early '70s I had a Majestic 16" round-screen b&w set whose picture did not fill the screen when the chassis was outside the cabinet. However, with the chassis in its normal position inside the cabinet, the top and bottom of the CRT were covered by the mask, so the picture looked round. (Round-screen b&w RCA and other sets also used this dodge to create a round picture from the original rectangular scan.) The raster only covered about the middle third or so of the CRT (again with the set out of the cabinet), so one could see the vertical blanking interval and its test signals (which also gave an indication as to when the station went from network to local programs--the test signals would disappear from the vertical interval during local broadcast time and return, of course, when the station rejoined the network). I don't know if TV stations and/or networks still use these signals in this age of microwave studio/transmitter links and network-to-affiliate satellite feeds but, IMHO, the test signals were fun to watch while they lasted (if you knew what they were and what you were looking at--most non-technical viewers didn't, and may have found them the devil of an annoyance if the picture shrunk due to weak tubes or other problems in the vertical sweep system).

BTW, the picture-size switch in the Zenith Porthole (a.k.a. Great Circle) TVs worked well when it worked, but the switch often caused problems with vertical sweep when the contacts tarnished or oxidized as the set aged. Many technicians simply bypassed or cut the switch out of the circuit when it acted up; my best guess is it wasn't missed that much by viewers, as it was just a frill anyway (another selling point for Zenith Great Circle TVs of the period). I doubt that most set owners even knew it was there. However, the TV worked just as well without the switch as with it.