Accurate 1 Hz Frequency From AC Mains

Line frequency is, depending on the country 50Hz or 60Hz. This frequency has small fluctuations in the short term, but is compensated daily by the power station resulting in a quite accurate frequency source for many timing applications.

Internal diodes protect CD4017B clock input keeping it within supply voltages. Schmitt trigger input allows for slow rise & fall times.

Absolute maximum voltage for CD4017B is 20V