police siren sounds , dub siren on strip board , anyone?

vibesmaster

i know its a bit random but i came across this place that built a siren effect box i just wondered if anyone wanted to shed some light on this schematic , i'm to much of a noobie to read it myself Embarassed

http://www.interruptor.ch/sirenschematic.doc

and also thought it might be interesting to some people on here as it makes sounds similar to the wsg heres a small sample of the sounds it makes

http://www.interruptor.ch/audio/RASTABOX.mp3

and heres the forum i found it lurking in ,

http://www.interruptor.ch/cgi-bin/discus/messages/1/111.html?1004083608

if anyone has a go at it let me know how it goes ,

any help with the schematic also apreciated,

zipzap · Posted: Mon Nov 06, 2006 5:28 am Post subject:

basically, what you´ve got here are two square oscillators.
The one on the right is making the sound, the one on the left is controlling the frequenzy of the right one. Since it is a square modulation signal you have the sound osc changing between two speeds.
P2 makes the whole thing sound higher or lower, p1 sets how fast the thing switches between the two pitches. P3 is responsible for how far the two pitches are apart.

BTW, if the modulation osc were a triange osc you would get the american, cojak type sweeping siren.