[ScanIndiana] ISP-51 two-tone?

[Jeff Howell]

The two-tone alert you heard is what is known as the Severe Weather and
Disaster Warning System.  It works the same way as two-tone fire paging, the
EAS, and similar alerting systems.  When an alert receiver "hears" these two
tones (I have those specific tones somewhere, if anyone wants them I'll dig
them out), it turns the audio on so that you will hear the voice
announcement that follows.  This is the same technology used by many fire
and EMS agencies.  Any pager or alert receiver on 42.42 or 155.37 with the
proper tones can be used.  Each ISP district has the capability to activate
the system; the same tones are used throughout the state.  Tests are usually
conducted every Monday morning at 10:00 AM state time.

In addition to severe weather information, the system is also used to
dissiminate other emergency action notifications.  You will occasionally
hear what is referred to as an "extend" test.  Each ISP district will
activate the tones, then each county within that district is called in a
roll call.  If the county heard the test, they will respond with "Brown
County extends."  What this means is that ISP passed the alert information
(whatever it might be) to each county in that district.  Each county in the
district then passes ("extends") the alert to other entities within the
county (law enforcement, fire, etc.).

Hope this helps.

Jeff E. Howell, EMT-B
Telecommunications Specialist
U.S. Department of Homeland Security
National Disaster Medical System
Disaster Medical Assistance Team KY-1