If you’re not familiar with the 555 timer, suffice it to say that this ... oscillator from nothing more than a Schmitt-trigger (ST) inverter, the resulting frequency accuracy will be poor ...

With a 555 on the BOM, you never know what you’re going to get. With 40 of the versatile timer chips in a build ... Luckily, the 555 makes a fine inverter too, and along with some diode-resistor ...