[TheList] Squawking Tones on Police Channel & High Frequency Tone on Channel

Sun Mar 20 12:07:11 AEDT 2022

Anywhere outside of Canterbury, Greater Wellington & Auckland are all still analogue. So can still be heard for a couple more years.

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From: TheList <thelist-bounces at radiowiki.org.nz> on behalf of Scott Matthews <ff.swatty at gmail.com>
Sent: Sunday, March 20, 2022 1:50:35 PM
To: thelist at radiowiki.org.nz <thelist at radiowiki.org.nz>
Subject: Re: [TheList] Squawking Tones on Police Channel & High Frequency Tone on Channel

Personally didn’t think most places could hear the police anymore?
Unless I am missing something?

On Sun, 20 Mar 2022 at 1:26 PM, Tim Devaney <timdevaneynz at gmail.com<mailto:timdevaneynz at gmail.com>> wrote:
Are we not going to be able to receive the police soon ??

On Sun, Mar 20, 2022, 12:09 DogSec - Richard <richard at dogsecurity.co.nz<mailto:richard at dogsecurity.co.nz>> wrote:

Hi BJ,

Years ago someone did a write-up about it on here, but basically it's a form of SCADA for monitoring sites remotely.  Some sites are often not easy to get to and may have access issues such as being helicopter access only.  These sites have quite large battery banks, as mains power may be flaky.  The SCADA allows for inputs and outputs to be monitored remotely.  They are often polled at specific times, which is why sometimes you may hear the tones underneath voice comms.  If the controller polls and doesn't get a response back then it will retry X amount of times (if programmed) then assumes the site is dead, and alerts get generated.  A variety of things can be monitored. Often these are only 'analog' inputs so you only get very specific details..  You could see things like

Battery Bank A is 100/75/50/25% (maybe not even in that much detail)

Generator On/Off

Entry Door OPEN/CLOSED

Alarm ACTIVATED/DEACTIVATED/IN ALARM

SOLAR ON/OFF (IE is there voltage coming into the system on the Solar lines)

REPEATER POWER ON/OFF  (some repeaters can have an output that's activated when it's in a certain state)  As Daryl mentioned, it would be a (probably unreliable) way of determining if a repeater is working or not.

With the NGCC being implemented, a lot of this will eventually become redundant as most things like SCADA would be converted to IP based, and digital radio is also IP based, meaning a lot of this could be sent over a text message over the radio network.  I assume P25, but DMR will prioritize voice over messaging.

As for the screeching, lots of factors could be causing that.  I-band links shouldn't really be used for monitoring as they're only point-to-point or point-to-multipoint links meaning you really need to be in line of the path for it to be received. I'd recommend use the VHF/UHF frequencies.  Once again, with things turning to digital soon, they'll probably be redundant with the links will be done over IP.

Cheers,

Richard

On 20/03/2022 11:23 am, Darryl Healy wrote:
Those tones are something to do with the linking with all the VTGs.

They happen every 4 hours at midnight and so on.

Someone will no doubt give a more technical explanation of them soon.

On Sun, 20 Mar 2022, 11:01 BJ, <bjcuizon151 at gmail.com<mailto:bjcuizon151 at gmail.com>> wrote:
Hi all,

Was in Dunedin recently and tuned in to police comms. Anyone know what those squawking tones on some police channels are? It doesn't sound like fire selcall but more like a really short (~1 sec) burst of what sort of sounds like a part of the old dial-up handshake.

Also, was listening to firecom and ambo thru the I-band link in Chch and on some link channels there is a really high pitched tone that is present when someone keys up. It can only be heard on a radio with no audio filtering/DSP as my Tait seems to cancel it out. Does anyone have an idea what this is as well?

Thanks in advance,
BJ
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