This circuit, from the 70's, can be assembled with a more modern FET like the BF245. The circuit is powered by a 9 V battery, as its consumption is very low.
This is the single-sourced version of the previous oscillator. Frequency can be changed by...
This is a commercial circuit found in Radio Electronics magazine from September 1960. The circuit has...
This circuit is from a 1998 Poptronics. The circuit triggers a buzzer after a certain time, waking...