Batboard

Okay, I just got off the phone with one of the guys down at the ambulance barn where I work at. Long story short, we are transitioning to P25 Digital. Not really sure why other than to spend $$$, however we are. I had brought up a while ago that our current station alert system, which sets off the horns and turns on the lights is a plectron, and would need to be updated since it is obviously not digital capable.

Their response? They want to buy a digital scanner and keep it in the crew room for us to monitor for calls.

I am looking for 2 things.

1. I know that there are NFPA requirements for station alerting for fire departments, is anyone aware of any for EMS/Ambulance dispatch? We are located in Connecticut.

2. What would people reccomend for an updated station alert decoder for P25. We use DTMF.

Thanks again, and I hope to try not and explode over this concept.

Some of the FD stations I am aware of have a base radio with a specific talkgroup to alert that specific station then the alerts are set off in house via relays off the radio. - So when a fire call goes out dispatch patches fd main with fd staion 1 or fd station2 and gives out the call.

makes sense. I need to crawl up into the attic where the old plectron is, and see what it is actually triggering the lights and horns.

Is there such thing as a P25 DTMF Decoder? I know they exist for analog...

Okay so I am a bit stupid. All I need is a P25 Reciever, and it doesn't matter what DTMF Decoder I use correct?

I am still looking for an all in one package vs. something I would put together myself.

I don't have a lot of experience with P25, but I am skeptical that the DTMF tones will pass through the Analog to Digital to Analog process without too much distortion. This could effect the reliability of your system!

WEC

uh....


"analog" DTMF is not compatible with the P25 bitstream.....






d

I would wait and see exactly what system they will be using for dispatch, they might even tell you exactly what equipment you'll need (better yet, they might supply it).

There are no specs required from the NFPA or the state of Connecticut.

A little know fact is that in the state of Connecticut, EMS is the only service that is required to have 2 way radios. One for dispatch, and one for ambulance to hospital comms. (Both have to be recorded.)

ohh no, they won't supply it...

Thats for sure.

I didn't even think that they would discountinue DTMF when they go Digital. The sad thing is when I brought up how we were going to be alerted at the station they were dumbfounded...and hadn't even thought of that.

Wile E. Coyote wrote:I don't have a lot of experience with P25, but I am skeptical that the DTMF tones will pass through the Analog to Digital to Analog process without too much distortion. This could effect the reliability of your system!

WEC

I may be a bit confused now...however here is what happening:

Dispatch, Rigs, and Portables are all going to be on Digital. What I was looking to do was take either a digital reciever, or radio and connect a DTMF decoder to it....

Is there a better idea that I could reccomend to our dispatch?

EOppegaard wrote:

Wile E. Coyote wrote:I don't have a lot of experience with P25, but I am skeptical that the DTMF tones will pass through the Analog to Digital to Analog process without too much distortion. This could effect the reliability of your system!

WEC

I may be a bit confused now...however here is what happening:

Not my area of expertise (yet) but I agree, putting DTMF though a digital system is probably not going to work well. On such a system you would want to use digital signalling, I'm not sure what your options are there though..

One thing they could do is leave a separate channel just for dispatch. Around here they've used a system for years where the two-tone station alert decoders and fireman's pagers are all on a lowband freq, while the portables and vehicle radios are 500MHz. They're now moving to a 500MHz channel for dispatch with digital pagers, but it's still separate from the voice communications system.

we call out our fire stations using a network connection, and we still have a 2-tone pager at each site for backup.

It might be a good idea to keep what you have, and just add the P25 equipment to it. Just to be safe

WEC

Every system I've ever seen used one of these:

-Conventional analog multicast carrying whatever signalling protocol is used.
-Trunked talkgroup dedicated to a particular station (Beaumont FD in Texas uses this).
-Alerting via MDT or other type of computer terminal (Houston FD uses this).
-Alerting via commercial paging service.

just another example of wasted money

Where I am in FL they upgraded to P25 as well but page outs remained on VHF.

RadioSouth wrote:Where I am in FL they upgraded to P25 as well but page outs remained on VHF.

That's what I've seen in so many systems. Either the old dispatch channel is kept and slaved to the alert talkgroup, or a new "page out only" conventional 800/900 MHz channel is added which serves the same purpose.

Alerting is too critical to trust to a less than totally failsafe system. You might want to review both these options with the powers that be, and see if a decision can be made. If you go with either system, make sure the page originates on the analog (conventional) channel and that all the levels are adjusted to make that channel trigger the Plectron boxes. The audio may be strapped to the P25 trunking system, but will only offer an audible message to portables, mobiles, etc.

There will not be any true decoding taking place on P25.

P25 will not pass DTMF or any signalling / analog data format. Too much warble. IMBE is a very poor codec. It cant reproduce accurately even human voice, let alone signalling where levels need to be more precise. Very crude. It is laughable because so many codecs exist that are free that are better (MP3 to name one of 100 or so) that will pass (or encode and then decode) DTMF and many other signalling forms. Why it costs a thousand dollars per radio/license is a mystery to me, and what is even more disturbing is that people accept it as good/are fooled. People see this as an "upgrade". I cant see one thing that is an upgrade about P25 fromv an APCO 16 compliant system. Most radio dweebs worship radios nowadays for what they look like and the hamsexy factor and not what they sound like.

motorola_otaku wrote:Every system I've ever seen used one of these:

-Conventional analog multicast carrying whatever signalling protocol is used.
-Trunked talkgroup dedicated to a particular station (Beaumont FD in Texas uses this).
-Alerting via MDT or other type of computer terminal (Houston FD uses this).
-Alerting via commercial paging service.

- Private POCSAG alphanumeric paging system. Fixed receiver at the station hooked up to a printer, and the usual alarm relays, with all the firefighters having standard Advisor II or similar pagers.

KitN1MCC wrote:just another example of wasted money

Exactly

I talked again with the board, and according to them they will discountinue use of analog, since "dispatch won't be able to do both" yeah...a crock

Anyways they claim that plectron makes a digital capable upgrade of what we currently have and they are looking into buying that.

they claim that plectron makes a digital capable upgrad

Plectron? I thought they went out of business back in the 90s...

they will discountinue use of analog, since "dispatch won't be able to do both"

So much for "interoperability".

/\/\y 2 cents wrote:P25 will not pass DTMF or any signalling / analog data format. Too much warble. IMBE is a very poor codec. It cant reproduce accurately even human voice, let alone signalling where levels need to be more precise. Very crude. It is laughable because so many codecs exist that are free that are better (MP3 to name one of 100 or so) that will pass (or encode and then decode) DTMF and many other signalling forms. Why it costs a thousand dollars per radio/license is a mystery to me, and what is even more disturbing is that people accept it as good/are fooled. People see this as an "upgrade". I cant see one thing that is an upgrade about P25 fromv an APCO 16 compliant system. Most radio dweebs worship radios nowadays for what they look like and the hamsexy factor and not what they sound like.

Finally, someone who isn't a fanboy lame-o spouting off about how their DSP makes their radio sound so good or providing better coverage footprints because someone told them it did. I saw some clueless putz on Ebay claim his DSP provided superior clarity over analog-- LOL! It is amazing how many sheep there are out there that believe what they are spoonfed, with no regard for the science or theory behind it all. I agree especially with your last sentence!

Anyways, I don't think MP3 is viable, how can you fit a decent sample rate into such a small pipe??? (12.5KHz or maybe even soon to be 6.25KHz)
Hell, they can't even get analog radios to sound good on 6.25. Besides, digitization of voice will always leave you with less than you started with.

CVSD with appropriate preprocessing sounds fantastic. With significant FEC, it's also very robust.

A DSP can make your audio sound better by removing noise etc (Codan Easitalk on HF for example), or do anything else it is programmed to do, such as digitise audio. In a Motorola VHF/UHF radio, as you've correctly pointed out, it won't clean anything up.

did they even look into the fact the NFPA and a few others have come out against P25 as a fire ground comms

also are the surrounding towns going to Upgrade to p25 i think not


gotta love NECS they will tell you what you want to hear and not lead you down the correct path unlike lets say Utility who rarely if never pushed p25 just uhf narrow band

up in middletown we have complete interop all agenc of the city on VHF and all the local town on UHF/LB but we have the radio to cover each other. they did not even want to hear about p25


also you dept needs to look into the fact they are not going to meet federal guidlines to be able to talk to other dept in your area they could loose and may have to pay back any grants

w8cmi wrote:Alerting is too critical to trust to a less than totally failsafe system. You might want to review both these options with the powers that be, and see if a decision can be made. If you go with either system, make sure the page originates on the analog (conventional) channel and that all the levels are adjusted to make that channel trigger the Plectron boxes. The audio may be strapped to the P25 trunking system, but will only offer an audible message to portables, mobiles, etc.

Down here in PA Montgomery and Bucks counties both have digital trunked systems and use VHF / low band (respectively) frequencies for dispatch. Montgomery county sends out tones only on the VHF than talks on both VHF and 800 (digital) for the dispatch.

A question it doesn't look like you've brought up is, are you guys going to P25 trunking or just P25 conventional? In either case, I don't see why your dispatch center can't leave some of the old analog dispatch equipment for alerting.

They told me Plectron, which I let slide since I thought back to my alert reciever I use as a door chock. I imagine it is made by someone else.

We are going to be operating on P25 conventional, not trunking. We will still have the ability to operate on conventional UHF in an alternate talkgroup. So there is some interop there...however not as easy.

Our main problem is the dispatch center is primarily for the PD, another discussion entirely...and their chief wants to go to P25. Since we have problem enough with the dispatchers being able to handle calls as it is, making them "push a button" on the console to switch over to an analog group would be "way too complex".

Yeah...and this is public safety

They could install an Astro radio and using the Call Alert feature, page the stations and using the Horn/Lights feature, have it activate the station's alerting equipment. I can't believe they want to use a scanner for alerting! What happens when some hammie keys down outside your station on the local repeater and it totally desenses the scanner and as a result, you guys miss a call?

I think almost all of the agencies here that have switched to a P25 trunked system here kept some VHF for fire paging.

I could go on about this "upgrade" that Eric is talking about for hours and hours and hours. As I'm sure you all can tell, it is the most absurd thing this group of incompetent baboons has thought up in years. When I heard of this "digital plectron", I almost slid out of my chair laughing.

The worst part about all this is that they were probably serious when they told you there was a "digital upgrade" for the plectron. They don't know any different, and instead of admitting they don't know, they rather make something up.

Another case in point why the "leaders" of theses cities should not spec. equipment for communications.

Which town is this?

I skipped thru some of the posts due to the usual bickering, but if you want to have something trip, they can:

-Retain a "paging" only channel to do things the usual way (many are doing this)

-Setup a specific radio (consolette would be a nice option) that will respond to a Call Alert / page command sent from the dispatch center in the P25 mode which can be used to trip relays. I have seen a couple of threads here in the past that have done this on conventional P25 and TRS systems.

Hartford has a similar setup, though the station alerting (alert packets) are sent on its own talkgroup - but the conept is the same - One radio sits on the alert channel to listen for their packet. When its heard, the lights and/or gong goes off.