SM3 2 SM3 2 INTRODUCTION TO THE SM3 The Ramsey SM3 will duplicate the sound of a police siren at a low (200 mw) or high (2 watts) volume depending upon construction. Closing a pushbutton switch will cause the siren to "wail" up in frequency and opening the button will cause it to "coast" down in frequency. You'll find plenty of uses for the SM3. Kids love to play fire truck or ambulance on their bikes and wagons (Mom will appreciate the low volume setting here!) and there are the obvious uses for alarms and alerting. PARTS LIST FOR THE SM3 1 .01 or .02 uf disc capacitor [if .01: marked ...
SM3 6 SM3 6 MODIFICATIONS HIGHER VOLUME: To increase the volume level, we add a resistor in series with C1 (that's why we have the holes spaced farther apart!) Simply unsolder one end of C1 and connect to R3, 1.5K (brown-green-red) as shown: YELPING SIREN: To make your siren sound like the yelping type (and get a tired pushbutton finger, too!), change C2 from 47 uF to a smaller value such as 5 or 10 uF. Experiment with different values for the right rate. You may find extra capacitors in old radios or other devices. If need be, you can even buy them new at Radio Shack for about 69 a pair! ...
. If you're missing five 10K ohm resistors and received five extra 1K resistors, ... much be assured that the '1K ohm' resistors are actually the 'missing' 10 K parts ... . If you're missing five 10K ohm resistors and received five extra 1K resistors, ... much be assured that the '1K ohm' resistors are actually the 'missing' 10 K parts ...