In use 9V source is replaced by patch from a buffered Eurorack synth output. Send the device about 3V it should oscillate. Vary that 3V to change pitch and stop start oscillation.
Use switch to get it going, or 'inject noise'.
421R resistor can be altered to simulate powering from un-buffered outputs.
Pitch varies with voltage.
2.2uF widens pulse into something more like a saw. From assorted unreliable internet sources.
(Search 'siren schematic')
150k is by experiment.
Change 68n to change pitch.
When direct connected to, e.g. a function generator things may of may not work.
