On Jun 25, 3:49*pm, " wrote:
Most anything that "flashes 12:00" is going to be using a crystal
timebase and not care about power line frequency. They flash 12:00 since
when they loose power they need to have the time set again, not anything
to do with line frequency.

Ah, no...

Anyone who has a device with a crystal oscillator timebase knows that
the device has to be reset to the correct time occasionally. *On the
other hand, plug-in devices that use the 60 Hz signal for the timebase
have been (up until now) essentially perfect since the signal has been
manually twiddled to make it so. *(There is actually a 10 second
tolerance in the East, less in the West.) *And implementation is dirt
cheap: *you capacitively couple to the power line, use a Schmitt
trigger, and some divide-by-60 counters. *With better performance at
less cost, using the power-line frequency as a reference is the
preferred method.

Thing become ambiguous in plug-in devices with "battery backup."
These devices do have crystal oscillators to ride out the power
outage. *When the power is on they can either use the crystal
oscillator as reference, or the power line as reference, however the
device was designed.

* * *- Jonathan

You are the first poster to actually get it correct. Thanks!!!