# Alarm Installation

#### TonyCollins

Sep 12, 2011
3
Can anyone tell me if the constant flow of 12VDC electricity through to 0V DC is a High (+12V) and Low (-0V) same as in Electronics.

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
I'm not sure I understand the question.

If you're asking if (in a 12V circuit) "would +12V be logic high and 0V be logic low?" then the answer is: "Probably, maybe". Much logic operates at lower voltages (5V, 3.3V) and applying 12V to their inputs may be a very bad thing. In general, 0V is logic low and the logic supply rail is logic high.

I'm not sure where you're going with the former part of the question, or its relevance to the second.

#### TonyCollins

Sep 12, 2011
3
Yes. Is 12DC Volts Logic high and 0DC Volts Logic low?

#### shrtrnd

Jan 15, 2010
3,826
Like *steve* said, common 'logic' circuits use 5V for 'logic high'.
There are some families of devices that can operate up to 18VDC.
Is this a theory question for homework, or do you have a specific logic family in mind?
(Is there a particular device in a particular circuit you're asking about?)

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