Re: switching (mostly) to digital


"Alan Browne" <alan.browne@xxxxxxxxxxxxxxxxxxxxx> wrote in message
news:L6gTe.44050$Wa6.548297@xxxxxxxxxxxxxxxxxxxxxx
> Brian Baird wrote:
>
>> In article <MPG.1d86a4ee6f10bcd9897fc@xxxxxxxxxxxxxxxxxxxxxxx>,
>> PunishSpammers@xxxxxxxxxx says...
>>
>>>BTW, unless you are too young or just ignorant, I suspect the latter,
>>>there once was a time where computers were analog.
>>
>>
>> They still operated in binary.
>
> No. Analog computers based on amplifiers, filters and feedback loops and
> other clever mechanisms were almost purely analog devices. They did have
> some discrete logic to activate circuits under some conditions or output
> conditions at a certain level would activate a discrete. Entire, quite
> complex systems could be designed w/o a single "binary" gate.
>
> A simple example would be a sensor that reads fuel flow via a turbine
> wheel in the fuel line, tracks the frequency of the 2nd harmonic of that
> signal (the tracker itself being a subset analog computer) and in
> proportion to that frequency turn the wheels on a "totalizer". No binary
> at all. It was all "by analogy".
>
> Early aircraft navigation systems even had a ball inside representing the
> earth and as the nav system (INS or Doppler Nav radar) sent pulses
> representing a small unit of easting or northing, the ball would turn to
> index its position. On the others side, so to speak, would be synchro
> outputs for lat/long. Seems bizzare, but did exist.
>
> Cheers,
> Alan.

There is a good discussion of analog computers, with examples here:
http://dcoward.best.vwh.net/analog/analog1.htm


.

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