I've built siren circuits using 555/556. Great two tone.
Trouble is I'm almost finished with a model fire truck of 2001 era and the modern equivalent 'yelp / wail / warble' is beyond me!
Does anyone know how I might start to get a handle on this?

I've thought of buying a 'blank' greetings card module and then putting a wav file onto it. But, 1) I can't find 'blank greeting card sound modules; and 2) Don't have a clue how to put the sound onto the chip anyway!
Previous help means I've got the knightrider LED sequence spot on, the blue lamps, head lamp, hazards are all working great. Just this last bit to go.

Do you have a schematic for your two-tone 555 circuit? Post it up and then someone can come up with suggested changes to make the pitch change smoothly instead of abruptly.

Or just google for "siren sound circuits".

Hi Kpatz,

The schematic is the one I've used - but it ain't mine!
I've also tried it with 556 and also with a Transistor.
The main issue is that modern emergency sirens seem to have a series of very rapid 'yelps' then a smooth sounding rise and fall (two tone ish) and then a few 'wails'! - The model is set to run lights, sound etc for 30 secs after pressing switch and ideally I want to get the whole sequence in.
Thanks for interest.

Many thanks but trouble is I no nothing about PIC!
I've Googled for PIC programmers and obviously they are easy to find, but where would a complete novice, that only worked in Qbasic, start?
Any thoughts appreciated, or can it still be done with a non pic solution?