#201 is a kit build. Ridiculously cheap on aliexpress, it even came with extra components, so a bit of a bargain impulse-buy.
The kit turned out to be a simplified version of a circuit I've built before. It lacks the power control circuit, and draws about 4mA when idle - so if you actually use it, expect to be replacing batteries on a regular basis.
As always, all notes, schematics and code are in the Little Arduino Projects repo on GitHub.
Here's the start of the "ding.." on a 'scope..
