Here's an IC used in some alarm clocks that uses the power grid's frequency, along with a list of products that use it: https://www.radiomuseum.org/tubes/tube_l

Here's an IC used in some alarm clocks that uses the power grid's frequency, along with a list of products that use it: https://www.radiomuseum.org/tubes/tube_lm8560.html https://www.radiomuseum.org/tubes/tube_lm8560.html