Spacewar! (was Re: Laser display...)

[Scott Stevens]

On Sun, 20 Feb 2005 12:02:49 -0800 (PST)
"Eric Smith" <eric at brouhaha.com> wrote:

> Sellam wrote about the Magnavox Odyssey game:
> > While the design may operate like a digital
> > computer,
> 
> It doesn't.
> 
> > it uses entirely analog techniques to produce the digital
> > results.
> 
> To some extent it's a matter of semantics.  Is a one-shot (monostable
> multivibrator) such as an SN74121 an analog device or a digital
> device? It uses an RC time constant (analog) to control the pulse
> width of a digital signal.
> 
> If you consider a one-shot to be a digital device, then most of what
> is in the Odyssey is digital.  Otherwise, one would have to consider
> it to use a mix of analog and digital techniques.
> 
> > Everything the box does is a result of analog circuitry.
> 
> So now your claiming that AND and OR gates are analog?  Most people
> would disagree.  Though in a sense you're correct, in that all digital
> circuits are constructed from analog circuits.  Design engineers
> forget this at their peril.  It's easy to think of them as ideal
> digital elements, but they aren't.
> 
> Eric
> 

At a medical device company I worked at, their 'first generation' TENS
device (neurological stimulator) used a single IC, a CMOS hex inverter. 
Several of the inverter sections were biased into an analog region and
used as 'analog' components.  The main multivibrator was made out of one
of the inverters.

Arguements about what is 'digital' and what is 'analog' inevitably
become (interesting) engineering discussions.

-Scott