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I'm trying to re-plumb a nice proprietary case for continued use with arbitrary motherboards. But I've no clear idea what the meaning of the small circles (shown in red, here) at the juncture of the traces is, or of the # chars on the descriptors.

I thought the circle might simply mean negation, as it does in gate symbols, but I'm not really confident that that's true, and it still leaves me in the dark about the # that terminates some of the descriptors.

Searching the web hasn't helped.

[EDIT] Okay, someone else asked about the circles (229425), and now I know that they do mean negation. But I still don't understand the #s.

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The default in logic circuits is that a high level (logic one) activates a function. The small circle denotes inversion, so we can have an external signal that is active low, which (when low) activates a function (that is still activated by the more-or-less theoretical signal after the circle, which is active high).

The fact that a signal is active low can be represented in various ways in the signal name, the # is one, and _ is another.

Don't be confused by the location of the symbol name, it denotes the external signal, not the internal signal after the inversion.

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  • \$\begingroup\$ Is there significance in some of the pins having both the circle and the # while others have only one or the other? \$\endgroup\$ – MMacD Feb 25 '17 at 15:55
  • \$\begingroup\$ Based on the labels, I guess # is being used in input pins and - used in output pins to clarify it outputs 0v \$\endgroup\$ – Marcelo Espinoza Vargas Feb 25 '17 at 15:59
  • \$\begingroup\$ Using an inversion on one wire in a pair is unusual, and I would call it bad style. LED- and SPKR- are not digital signals, so they're not "active-low" in any meaningful sense. \$\endgroup\$ – Adam Haun Feb 25 '17 at 16:13
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It's as you stated, negation gates.

They use this to tell the user that the pin is active when applied 0V,so to keep it deactivated you must set a +Vcc voltage in the pin.

The sharp symbol is exactly the same you can see that sharp symbols and circles coincide on the same pins.

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Both the circles and the # imply negation, i.e. that the signal is active low.

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