Why 48 holes for the Camera/Monitor?

[Viewmaster]

I wonder, please, if anyone can explain why the camera/monitor construction described in Chapter4 of the handbook on the NBTV website needs 48 holes?
As the camera is on one side of the Nipkow disc and the monitor is on the other side of the same disc I would have thought that just 32 shared scanning holes would be sufficient.
I'm obviously missing something here, but cannot think what.

The page is here......
http://www.nbtv.wyenet.co.uk/cam-mon.htm

.....and the write up says......
"The club disc has a spiral of 48 holes over 1.5 revolutions. The camera masks the inner 16, the monitor the outer 16 holes. In this way the camera and monitor share the same disc. There is an extra circle of 32 sync holes at the rim."

BTW, the reason I call myself 'Viewmaster' is not that I am a master at anything in particular but just that I built the "Viewmaster" 405 line TV kit way back in the late 40's ! Now I've given my age away!

Albert.

[Stephen]

The reason for the extra apertures is because the monitor display is 180 degrees out of phase on the scanning disc and also that the scanning area are on opposite sides for the camera and display. In other words, by having a spiral of apertures that extends for 1.5 revolutions, as the first aperture at the "beginning" of the spiral appears in the camera scanning area the first aperture at the "end" of the 1.5 revolution spiral appears in the display scanning area.

Without this arrangement, the display would show an image split in two, with the left half of the picture on the right side and the right side of the picture on the left side, since as the camera starts scanning one frame the corresponding aperture on the display side would be mid-frame. This is all easier to visualise if you draw a disc with a 1.5 revolution spiral with rectangular scanning areas on each side.

Actually, if I were to build a camera I would dispense with the built-in monitor. There are enough complications for a beginner even with a standard scanning disc.

[Viewmaster]

The reason for the extra apertures is because the monitor display is 180 degrees out of phase on the scanning disc and also that the scanning area are on opposite sides for the camera and display. In other words, by having a spiral of apertures that extends for 1.5 revolutions, as the first aperture at the "beginning" of the spiral appears in the camera scanning area the first aperture at the "end" of the 1.5 revolution spiral appears in the display scanning area.

Thanks for that which I follow.
A combined camera and monitor would be rather nice especially if the camera were reversed to shoot forward. This would make it a kinda NBTV single lens reflex camera.
Albert.