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

Sun Mar 20 11:24:43 AEDT 2022

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>
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> 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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