Fri Dec 15, 2017 2:25 am
The E57 is a 9 port siren, so it does 425 Hz when on 50 Hz AC. They do 530 Hz on 60 Hz like a Screamer S-5.
These sirens actually had speed control of some sort on the chopper motor which is why they have such a linear wind up. Battery voltage would only affect how fast the chopper would ramp up. Most of them tended to be somewhere in the 415 Hz or 425 Hz area so long as the batteries were in good condition; if the voltage falls too far below 24 VDC it would have slow wind ups and peak lower than normal just like any typical DC powered siren. When that speed controller or whatever it is gives up the ghost, the chopper will spin up and run at any pitch. Cologne has 273's like that that sound like 508s and T-128's in the distance, roughly 485 Hz at full speed with one that likes to peak out at around 530 Hz.