The 60hz mains are accurate only over long durations, like a day or so. From what I've read, they adjust the frequency occasionally to make the total number of cycles accurate over time, but on a moment to moment basis they may be off.
Crystals are usually pretty precise (compared to oscillators or resonators), check the spec. So - mains are more accurate, crystals are more precise. Also, my furnace project has a circuit to detect zero crossings in the 60hz mains (through a 24vac transformer) if you need it. _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
