Police Siren

I've just put together this circuit and all I'm getting is a single intermittent note, part of a two tone. Certainly not wailing. Any ideas where I've gone wrong? Made sure all the components are secure and that the circuit is as shown on the schematic. Unable to upload a photo of my circuit constructed on a breadboard, message just said file too large doh!! Any idea moderator why a single photo is too large to upload?
Konrad :eek:
I think this forums limit is 50kb. Try uploading it onto a different site and just post the link on the forum. If you're already trying on another site, tell me what the file size of the photo is and I can help you more.


Staff member
Hi Konrad,

I have just increased the file upload limit. Please try to upload your photo again.

Thanks. I have found where I went wrong with this circuit. For some reason I had put two links in between pin 3 of the first ic and pin 5 of the second ic, one with the 10k resistor and the other without, that's why I was only getting the single tone. I've removed the one without, works fine now. I have made a few changes and have come up with a much more realistic sound, not so much the tone but the speed between tones. Substitute the 68k resistor between pins 6 and 7 on the first ic with a 100k resistor and it slows the sequence down just enough to give a very realistic experience. Almost like being back on the fire engine. One other mod I have made is to place a plastic container over the 8 ohm speaker held in place with a 'lacky' band. I will try and post a picture of the set up later on. It would be good if the size could be increased to accept video as well. I'll try it just in case it accepts it. auf wiedersehn,

Konrad ;)
It's still constructed but I'm not sure that it will be of a size acceptable for uploading here. Videos, even short ones take a lot of space. Perhaps the moderator could give us advice on whether or not a short video would be ok.

Konrad :confused:
Got it to work as shown with the two 555's and also with the 556... Inserted a 1k pot between the second capacitor and the speaker for volume control... Worked great...
sorry admit I tried connecting the circuits according to the schematic diagram but it only gives me a 1 sound not a two sound... can you help me please admin.... I am trying to get this work.. please..
Hello to to you all,
I am quite new as hobbyist to small electronics so please be gentle with comments.
I have tried to assemble the shown "police siren" circuit with 9V battery (10k, 68k, 1k to bridge the two ne555 and two 1k for second NE555 with 104 and 10 microF) and I have no sound out of speaker.
Here is my breadboard. I would be trilled if anyone could help me out to solve the problem.