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Another question involving a monostable.

This is the one I like, only I'd feed the three digital signals to the address pins of a CD4051 (8-to-1 analog mux) with a

8-tap resistor string on the eight inputs, and feed the output through the wire. That's the DAC.

At receive end, a small ADC gives out (as its three most significant bits) the state of the three inputs. To keep noise margin high, you'd want the resistor string to have taps at 4.5 for binary 100, 2.5 for binary 010, and 1.5 for binary 001, and the full range of the ADC would be 8.

This would be a great place to use a little five-bit flash ADC.

The non-overlap of the multiple pulses is a don't-care condition.

Reply to
whit3rd
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Perhaps. With just this much description of the problem i would most likely try some thing like this:

Use the signals to generate touch tone dialing signals with a standard IC and detect them at the other end with decoding SW running on a small micro at the other end. This works well so long as there is not an interfering combination at the same time. Otherwise you could just use the same 3 frequencies from just the high band. Might simplify the detection algorithm a bit. Of course you could use discrete detectors as well.

?-)

Reply to
josephkk

Hmmm. All CMOS inputs need to be terminated high or low, unterminated inputs can oscillate or may turn on both n and p channels at the same time and over dissipate the device or cause localized heating fractures.

?-)

Reply to
josephkk

What's wrong with that? :)

Jamie

Reply to
Jamie

Yes, everything, none of that will work reliably.

Reply to
bloggs.fredbloggs.fred

resistors,

code

want

be 8.

Bah-humbug. You don't need no old CA3306s, common cheap SAR type ADC will get the job done in less than a dozen microseconds. Way fast enough for millisecond tolerant systems.

?-)

Reply to
josephkk

Both versions work reasonably well, but provide subtly different properties. It is worthwhile studying the difference.

Reply to
josephkk

time

I installed pop-off legs for people that liked to pull my leg. You haven't reached pop-off level this time. Sorry, no game.

?-)

Reply to
josephkk

Care to expand on that?

Reply to
Pimpom

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