SDPD Dispatch

[JoeyC]

Is it just me or has anyone else noticed that it appears the San Diego PD dispatchers are either using a new type of digital headset or something has changed in the dispatch center? The dispatchers, (I've noticed this especially with central and northern) sound very "digital" today. Much like what patching from the digital RCS sounds like on the analog talkgroups. Or has there been some other hardware or software changes to the Smartzone system?

 

[K6CDO]

Is it just me or has anyone else noticed that it appears the San Diego PD dispatchers are either using a new type of digital headset or something has changed in the dispatch center? The dispatchers, (I've noticed this especially with central and northern) sound very "digital" today. Much like what patching from the digital RCS sounds like on the analog talkgroups. Or has there been some other hardware or software changes to the Smartzone system?

It is not just you. The City cut the 800 MHz SmartZone infrastructure over to their P25 core yesterday morning. PD and FD console audio now has a slightly different routing to the radios.

Don

 

[JoeyC]

Thanks Don, I knew something had changed.

 

[Anderegg]

SDFD Dispatch is "digital" sounding now as well.

Does this mean San Diego's TRS is going P25 soon? I would really like to know if it is because I am using old 780XLT radios for it now and will need some lead time to order some new 996XT's to replace them if SD is going digital!

Paul

 

[K6CDO]

SDFD Dispatch is "digital" sounding now as well.

Does this mean San Diego's TRS is going P25 soon? I would really like to know if it is because I am using old 780XLT radios for it now and will need some lead time to order some new 996XT's to replace them if SD is going digital!

Paul

Not at this time, Paul. The only change currently is the 15-year old computers behind the trunking magic have been replaced with modern ones. The mixed-mode trunking protocol is still the Motorola SmartZone 3600 baud control.

Don

 

[JoeyC]

Does this mean we are not going to have as much talkgroup bleedover that plagues the system?
I don't expect that the old Emer tone will ever return eh? I sure miss that silly thing!

 

[WayneH]

PD and FD console audio now has a slightly different routing to the radios.

I'll translate for Don. The old consoles used copper wire and analog routing of audio so there was minimal digitization (the only digitization was over the backhaul but treated as a traditional DS-0 digital circuit). Modern dispatch consoles are now using IP and therefore force the audio through DSP/lossy codecs.

And without knowing what truly happened with the fixed end equipment I think it's safe to say the bleed-over should be rectified.

I'll miss the repeated DTMF 8 too (I think it was DTMF 8?). I cut teeth listening to SDPD on VHF.

 

[Anderegg]

So they have effectively "upgrade" to the much hated "digital" audio....that makes a lot of sense. My cell phone can upload data at 14Mbps, yet the future of digital radio audio is like 9 micro tiny bits per second....ugh.

Paul

 

[inigo88]

Did they make the switch from Centracom to MCC 7500, or was it something else?

 

[jmarshl]

I have been told that the old emergency traffic tone was DTMF 9. There is hesitation to re-establish the tone due to problems experienced when other trunked systems tried it. Reportedly a system in Texas locked up when they tested their emergency tone.

 

[K6CDO]

Did they make the switch from Centracom to MCC 7500, or was it something else?

No changes yet, although MCC 7500s may be in the future.

 

[inigo88]

I'll miss the repeated DTMF 8 too (I think it was DTMF 8?). I cut teeth listening to SDPD on VHF.

Haha I never put two and two together that the emergency tone was just a DTMF 9 repeated four times in rapid succession. It seemed so different from the usual "Code 33" tone used by CHP and most of the Bay Area agencies, I thought it was a custom thing.

I'm still not sure what the P25 core is exactly, so I'm guessing something between the CEB cards for the Centracom consoles and the microwave backhaul? A bunch of IP routers and cat 6 cable? I'm sure I'm missing a few dozen (or hundred) components in between.

 

[Anderegg]

The SDFD 3 tones before the dispatch even sounds digitally......it sounds so flat and lifeless now, I want the old analog beeping that doesn't sound like R2D2!

Paul

 

[K6CDO]

Haha I never put two and two together that the emergency tone was just a DTMF 9 repeated four times in rapid succession. It seemed so different from the usual "Code 33" tone used by CHP and most of the Bay Area agencies, I thought it was a custom thing.

I'm still not sure what the P25 core is exactly, so I'm guessing something between the CEB cards for the Centracom consoles and the microwave backhaul? A bunch of IP routers and cat 6 cable? I'm sure I'm missing a few dozen (or hundred) components in between.

Exactly.

 

[WayneH]

So they have effectively "upgrade" to the much hated "digital" audio....that makes a lot of sense. My cell phone can upload data at 14Mbps, yet the future of digital radio audio is like 9 micro tiny bits per second....ugh.

It all comes down to bandwidth. The idea is to make the most efficient use of the bandwidth available to you (with a balance on hardware) but at the same time providing voice quality that is intelligible. People can get used to the stretched tones in the voice. Digitizing as much as possible uses less bandwidth (which increases your total available capacity) and less resources.

For example, I work with a lot of 10GHz microwave radio. With a 30MHz wide carrier I get 160Mb of total bandwidth to work with. Due to overhead I end up with close to 150Mb in reality. Compare that to an in-home Gigabit network (I can do 800Mb+ with the right conditions) and it sounds ancient. Once you go over the air you cannot match the capabilities of true wired connectivity. The point I'm getting to is the majority of what creates a wide area trunked system is done through wireless backhaul. You want to make the most efficient use of what you have so it gives you more ways to use it.

I'm not sure what the scare is with DTMF. The only issues you have are in digitizing DTMF, which doesn't work. It needs to be in-band. With P25 what they do is pass the tones as signaling data then make the receiving devices translate those in to true DTMF tones. The actual tone is never transmitted. So sending a DTMF tone only results in a poor sounding version of it.

 

[Anderegg]

Compression for audio and video have come a LONG WAY since Motorola and APCO came along.....I think a huge change is needed, but that would probably be too complicated to change the entire infrastructure of the current digital radio systems.

Paul

 

[WayneH]

Compared to the rate of improvement of compression quality I think voice digitization has made greater advancement. Two-way radio has always been too slow in keeping up with technology.

 

[Anderegg]

I just think that it is sad that two way radio voice quality was more superiorer in 1960 than it is today!

Is superiorer a word? :-\

Paul