Seven Segment Displays

[Tony Duell]

> I saw some at a hamfest. I lost my interest as I figured out that they
> operated the same way as most VCR displays.

Not at all!

The Minitrons are incandescent displays. The light comes from a hot 
filament wire, like a light bulb.

Most VCRs (at least over here) use vacuum fluorescent displays. They're a 
bit like directly heated triode valves with fluorescent compounds on the 
anode (plate). There's a filament (or two) across the front of the 
device, operated below red heat, so you don't see it glow. The anodes are 
the shape of the segments and other symbols and glow when hit by 
electrons emitted by the filament. And there's a grid between them. 
Normally corresponding segments of the various digits are connected 
together inside the device, the grids are used to select a particular 
digit -- it's a stnadard multiplexred drive.

[One of my VCRs has a load of LED 7 segment displays on the front, but 
that's another story...]

-tony