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

Sun Mar 20 11:50:35 AEDT 2022

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> 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>
> 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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>>> TheList at radiowiki.org.nz
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>>>
>>
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