The Siren Board

Here is the old NYPD sirens from the 80s, and early 90s http://www.youtube.com/watch?v=ED3nol_lcN0 Awsome!!! only thing is that it seems it would not be as effective holding at peak like that during wail.

All NYPD sirens still feature the "Momentary yelp" tone, as well as immediate cessation of a tone (i.e., the wail doesn't coast down). Many PA300's were simply rewired to accomplish this.

JasonC wrote:All NYPD sirens still feature ... immediate cessation of a tone (i.e., the wail doesn't coast down). Many PA300's were simply rewired to accomplish this.

I like that.
I press microphone button to instantly silence Wail and avoid the 4-second coast down.
This saves the ears of pedestrians at whom the speakers will point as I am turning, plus, by that time, the siren sound is not needed anyway.

How do they accomplish immediate cessation?
Thank you,

By simply cutting off the current to the driver.

I'd imagine some older controllers were designed without this in mind, all you need is a new controller.

Justin Savidge wrote:By simply cutting off the current to the driver.

No.

To achieve immediate cutoff, you simply ground one of the legs of the wail capacitor (C-24?? I cant remember without looking at the PC board). I dont have my schematics anymore but I've modded several PA300's this way and even included phaser override capability.

I slightly slowed the Yelp on our Unitrol 800 by adding capacitance.

But they would not approve of making any alterations such as a switched ground to the Wail capacictor.

If anything ever fails, though totally unrelated to the unauthorized alteration, they would void any warranty.
(But I have never owned ANYTHING which was even close to being within the warranty period!)

I just use the microphone switch.
But the sound generation circuit continues to cycle, so when I let the mic switch go, the siren emits whatever part of the cycle it happens to be in.
Example: It may be sound at the top and then descend.