On: System separation in the Continental Europe Synchr...

[garaetjjte]

I don't think price is significant factor. It just needs optocoupler, diode and few passives.

[klodolph → garaetjjte]

You don’t need an optocoupler to measure grid frequency. You can just use a resistor. Dirt cheap, cheaper than a crystal.

[garaetjjte → klodolph]

Yes, but OP talked about isolated circuits. It's likely that most appliances don't need to be isolated though.

[klodolph → garaetjjte]

OP was talking about consumer circuits, I think they were mistaken about how likely they are to be isolated.