> My estimate of the citizen ecodrives automatic rate adjustment occures at 10 day intervals. That only works if you can track the signal continuously. Suppose you lose the signal for a while. How many cycles was that? If it's only a short while and your clock is stable enough, you can assume you will come back on the right cycle and only be off a bit on the phase. Your clock stability determines how long a "short" while is. Now consider that your watch will be out of contact for 8 hours while you sleep. If it was accurate to 1 cycle in 8 hours, you wouldn't need to go through this much effort to calibrate it. This is similar to the problem of RS-232 clock accuracy. The receiver needs to be able to determine the difference between N and N+1 identical bits. -- These are my opinions, not necessarily my employer's. I hate spam.