Electronic Siren

If there is one sound that is recognized almost universally it would be the wailing of a siren. Police use them, other emergency services use them, burglar alarms use them, people stop and start work to them, air raid warnings use them.
An electronic version of the old mechanical siren is very easy to make. Here’s how:

You will need these components
Resistors:
One 47 ohms (yellow – violet – black)
One 68 ohms (blue – grey – black)
One 33k ohms (orange – orange – orange)
One 47k ohms (yellow – violet – orange)
Capacitors:
One 0.1uF polyester (‘greencap or MKT’)
One 100uF 10 volt electrolytic
Diodes:
One protection diode (1N4002 or similar)
One light emitting diode (LED)
Transistors:
One NPN type DS548 or similar
One PNP type DS558 or similar
Miscellaneous:
One battery clip
Six lengths of plastic insulated hook-up wire, approx. 12 cm long
Six lengths tinned copper wire
21 self-tapping screws with washers
Baseboard and project overlay No. 6