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@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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