These two headlight reminder circuits are easy to install and operate on the KISS (Keep It Simple Stupid) principle. The simple circuit involves adding just a 12V piezo buzzer between the lights ...

Here is a simple freezer alarm circuit, but ultra sensitive with a buzzer. The circuit raises an audio alert when the temperature inside the freezer box goes up above a preset level. The circuit ...

The flashing is thanks to LEDs with a built-in, integrated flashing circuit and the nasty noise comes from a piezoelectric buzzer — both are available from electronics stores that sell ordinary LEDs.