[TowerTalk] TowerTalk Digest, Vol 133, Issue 49, siren

[Patrick Greenlee]

In the olden days back before Radio Shack became a cell phone boutique they 
sold DIY alarm components and systems which included electric motor driven 
siren (cast aluminum horn and rotating component) using the equivalent of an 
automotive heater fan motor.  These things were very loud but had a slight 
drawback.  You needed to drive them intermittently as when fully run up to 
speed the sound emitted was very high pitch into ultrasonic.  Running them 
intermittently a few seconds on and a few seconds off gave a sliding tone 
WAILING that was an attention getter.

Now days solid state systems have essentially replaced most motor driven 
sirens. Reliability?  I don't know, my sirens are 40-45 years old and still 
work perfectly.

Don't forget a good strobe light to attract attention at night. Nefarious 
activities tend to favor quiet and dark.  Loud noise and bright lights tend 
to deter nocturnal mischief. Even IR operated security lights help.

Patrick NJ5G


-----Original Message----- 
From: Spencer
Sent: Tuesday, January 21, 2014 10:58 PM
To: towertalk at contesting.com
Subject: [TowerTalk] TowerTalk Digest, Vol 133, Issue 49, siren

I have a LOUD one, 12" diameter and a automotive starter motor spins it.
Quite effective!
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