The circuit design and Arduino code for this project are copyright 2010-2011 Andrew Back and licensed under Creative Commons Attribution-ShareAlike 3.0 Unported. For further details see:

 http://creativecommons.org/licenses/by-sa/3.0/

Note: this does not imply any rights to the artwork entitled "Time for Tea?". What this means is that you are free to use the circuit design and source code under the terms of the licence, but that you can't use them to make copies of the artwork.

The Arduino code is based on an example from Jean-Claude Wippler at:

 http://jeelabs.org/2009/05/28/measuring-the-ac-line-frequency/