Use sine waves, and try 2 seconds for A tone and 3 secods for B. Honestly, I'm not sure exactly how the Federal decoder is designed but it might be worth a try to reverse A and B. Some coding plans refer to the B tone as the common tone.

Are you using the common tone as your first (A) tone or your second (B) tone? Also, what are your tone durations and gap (if any)?

If you can hear the tones you are sending through the speaker then the receiver, CTCSS circuit, and antenna are all OK. This test doesn't verify the receiver sensitivity, but it should close relays if the decoder matches your generated tones. The two tone decoder pictured uses L-C filters which migh...

I have restored an few sirens, including a Sterling M5. The main problem with older Sterlings is that the motors were not designed to hold up to weather without a good cover, and as the sheet metal in the covers rusted away over the years the motor windings and bearings become damaged. Some older be...

Lots of equipment had the CD emblem back in the height of the cold war. I think it had to do with civil defense funding but I'm not really sure.

We had a Motorola Twin V in our 1951 Mack engine but it was scrapped when the (relatively) newer GE MASTR Pro was installed. Thanks for sharing.

If a chopper has n ports, it will produce n pulses of air for every revolution. Multiply n by the number of revolutions per second and you have frequency in Hz (pulses, or cycles, per second). Since most motor speeds are given in revolutions per minute (RPM), you must divide motor speed by 60 to get...

... I'm thinking the "beat" effect is for the purpose of better getting the attention of people across a wider range of effective hearing conditions,.. I agree Peter. I read somewhere that the original EBS (Emergency Broadcast System) alert tone ("the attention signal you just heard ...

A good question. Lots of equipment has been designed with dual power sources over the years (buses, boats, sirens) with varying degrees of success. The toughest part is getting the motors to work well together. All sirens will have small variations in bearing friction, winding resistance, air flow, ...

... there was a siren from the mid 70's to early 80's ? that had the wail/yelp together...I think it may have been a Southern VP? don't remember... it's been a while. You're right, there are some that do a dual wail/yelp. I have heard them in ambulances around here, but I don't know the manufacture...

Thanks for posting the link, it really took me back in time :D Most electronic sirens of that vintage used a pair of analog oscillators, one to generate the siren tone and a second to modulate the frequency. Changing the selector from wail to yelp switched in different resistors and/or capacitors th...