Batboard

Ok, this is going to be a pretty long post, so if you need to grab a cup of coffee or something, better do it now...

I have a customer currently with a Centracom II Console with (get ready for this....) 11 channels simplex on the same freq....ok...these sites are currently voted to provide the best audio to the dispatcher. To keep redundancy in case the voter fails, we installed a seperate remote monitor speaker that listens to voted audio, and the dispatchers keep their select/unselect volumes turned all the way down on the Centracom II, and in case the voter failed, they just turn them back up, and they are back in a conventional operation.....

with me so far?

Well, now they just bought a Zetron 4048 that I am building in the shop now. The customer now wants the following features that are a little different from his current configuration:

- voted audio in select speaker
- voted audio in headset

and the ability to still revert back to wireline rx audio....


btw, this is my FIRST 4048 install...so i am open to ANY ANY ANY suggestions....

Ok, i am working with another tech who has YEARS of experience over me and any other tech of the shop, but we have bumped heads a couple times about this whole project...and he isnt really familiar with zetron either, mostly moto stuff..
'
he had a few ideas:

- we could run them in the same operation they are now, select/unselect all the way down, and use a monitor panel for voted audio....

and i shot that down because:

- no sidetone audio , no error beeps, no recall recorder playback or any other audio would come out of the sel speaker. and if they talk on the other channels that are not voted such as intercom or orderwire to the microwave sites, they will HAVE to turn up their sel or unselected audio, and now your hearing rx wireline anyways...defeating the purpose of this vote situation...

- and there is no audio in the headset, which is what the customer wants...


so he comes back with:

-using the aux audio on the back of the 4217, which brings audio into select speaker and headset...

and i shot that down because:

-ok, now you have voted audio in your headset and select speaker, which is GREAT, but you also have whatever site you have selected as well, summing those audios together...which if you dont know the voting condition you may be listening to another site that is out of phase..


so here is my idea, and i would like some feedback to what i came up with...

the customer really only cares about 3 audio sources: voted, intercom, and orderwire.

i could run voted audio in on a channel card for RX only, but, i KNOW we will be back to fix it because someone sometime will try to PTT on that Rx only channel...and i dont wanna be the one running that 2am service call...

however, i was looking through programming and found a MAIN/STANDBY feature, and by doing some research I found that there is AUX OUT per channel on the channel punch blocks that pulls a ground when an individual channel is in STANDBY.

So I drew this up:

put in 11 relays, DPDT. make this relay pull in when its corresponding channel is in STANDBY.

on the common side will be the rx audio to the channel card

on the n/c side will be voted audio

on the n/o side will be regular wireline rx audio.

..

i do forsee loading the audio from the voter quite a bit, which could be fixed by cranking the inputs up, but when you go back to wireline you wont have that load there so you regular RX audio will be hotter than ..well you know...

so i talked to the customer about installing a audio distribution amp, and they agreed...

now, so if the voter takes a crap totally, you just reach up and select a site at a time and click it to standby, which brings rx audio back...or if you lose one card of the voter, just enable that channel you lost.

this will give them:

-voted audio in the headset & select speaker no matter which site is selected (other than intercom and orderwire of course)

-they can keep their sidetones and encoder audio

-they can instant recall record just one site to go back through and review rx audio instead of digging through 11

-the redundancy of bypassing the voter


they do however lose unselect audio...but they dont have it now anyways...

and if i have to run the orderwire and intercom to a monitor panel i can.

i bought high quality relays for this project, with LED indication so i can instantly see if someone has goofed and has a site in standby when it shouldnt be... and also they have a manual switch so if the coil fails i can switch it to wireline rx audio in the event of an emergency...


my problem with this is I am YOUNG, just turned 19 this christmas, so trying to make this idea look appealing to a bunch of moto legends is kinda difficult...

and they think that my way is un-conventional...but from the information i have provided you can probably agree this is a non-standard installation with 11 sites simplex and voted..

i guess what i am really looking for is a "yeah thats a good idea and it will work" or a "thats the stupidest thing i have ever heard of!"

thanks,
Nick

Nick -

Wow. What a cluster.

I'll lecture first. Then try to help with the technical problem.

First: Don't let them snow you about the "Moto legends"; I'm willing to bet dollars to donuts that this came about as the result of years of back-room engineering, dealing with what was wanted and then having to factor in what COULD be done, and by now you've got.... a Mongolian Clustergaggle. Well, that's probably an insult to Mongolians.


Next question is, what kind of voters are these? After re-reading your post, I think I'm seeing that they want to be able to select a site, even if it isn't the one that's 'VOTED BEST' (sorry, that's supposed to be redundant - if the voter has decided it's the BEST QUALITY, that's the definition of VOTED.

(BTW, if the audio presented as VOTED is worse to your ears than another site, the system probably has deeper problems....but that's another kettle of fish)

For example, JPS voters, & GE voters as much as I can remember about them, you can FORCE-SELECT a site. I have to believe you can do this with Moto voters, too;

Still seems very bizarre to me to care about those 3 audio sources; voted, intercom & orderwire.

And is this system you're building - is it just for these 11 channels, or are there other channels mixed in ? [Which if yes, will make things even hairier.... : ) ]

I guess I'll have to look at my 4000 books again (a good idea since I'll be doing some hands on on one soon, too) and keep your issue in mind.

Chuk G.

yes, i do believe you insulted the mongolians...lol


anyways, the voter is a doug hall, and i am a jps guy all the way...i have barely messed with a doug hall...so i am not sure of its capabilities but i am sure force select is one...


i think maybe i havent explained the situation as well as i wanted...
the only reason to select a site would be to transmit, and in my scenario there would never be a chance for one audio to be better than another.... the system we are dealing with is spread about many counties, but the voter still usually elects 3 or 4 sites during a mobile field unit tx'ing....

the only channels we are dealing with now is the 11 voted, intercom and orderwire...but i know for a fact this willl change in the next year.

i am almost 99% sure this setup will work using the MAIN/STANDBY ...i am just looking for some muscle to say "yeh that will work" because like i said earlier....i'm young and its hard to make a point with a shop full of guys with 20x the experience i have...

thanks for the input though...and if you need anything explained in detail i will be happy to do that...

-nick

I want to think about this a bit, but let me ask a couple of questions:

1. What type of Channel Cards are you using? And do you have a pin/pair number on the channel card punchdown block for this "Main/Standby" thing you're describing (which, I have to say, is news to me).

2. Use of relays is hardly whacky. It is the standard way of steering to a standby xmitter in voted repeated systems, and if you PM me a direct email address, I'll send you a write up of using it in a slightly different application.

3. If I understand properly, customer has 11 receivers (all same freq/tone) and 11 transmitters (all same freq/tone); audio from all receivers goes to receiver cards in a comparator. Also 11 console channel cards? Where does Rx output from comparator go? and how does operator select which xmitter to xmit on?

4. Take a look at the Zetron "1 of n" feature. Allows you to program n "buttons" so that selection of 1 of them cancels the others. You could, for instance, program 11 I/O buttons to pull in a relay that connects individual receiver audio to common path (for instance, Ch. 2 card Rx line) and 11 other I/O buttons to direct Tx output from common path (for instance, Ch. 2 Tx line) to an individual xmitter. In essence, Ch. 1 would be comparator voting and Ch. 2 would be operator "voting".

5. Mixing Rx audio from same freq/tone on different console channels, I would think, would pose an additional problem: if you xmit on one channel (selected) and your own voice comes back to you on another (unselected) channel, you risk a cascade squeal. How is this dealt with?

(Take a look at the X-Busy-Out and X-Busy-In signals on the channel card. If the channel card is transmitting, it pulls X-Busy-Out low, so that you can use this to stifle a simultaneous PTT from a parallelled remote or other device. Likewise, if X-Busy-In is pulled low by some parallelled device, it prevents the channel card from simultaneously transmitting. By programming (from memory, via the feature switches on the channel card itself), pulling X-Busy-In can also be made to mute the audio on the channel card.)

6. I have to say that all of this seems a lot of work to deal with hypothesized "comparator failure." In my experience (almost exclusively repeated systems with several receivers and one or two transmitters), the most likely failure is a phone line, followed by receiver itself, followed by receiver card (SQM). If the activity monitor doesn't deal with this itself (failing a receiver if loss of status tone followed by no voice within X seconds), you deal with it manually by failing the receiver from the comparator control panel. I don't think I've ever seen a failure of the comparator cage or control module itself, and if this is a concern, why not just spare those cards?

Don't know if any of this helps.

Thanks for the input!

The Main/Standby feature is located on the individual channel in the RDPS programming. There is a bubble that says GENERAL or MAIN/STANDBY. By Clicking this it not only gives you a visual on the individual channel on the touch screen, but also the ability to change it to standby after you program a button called main/standby..

On the channel punch blocks there is an output called "AUX OUT" that goes low when your channel is in a"STANDBY" condition.

Also, dealt with the feedback issue... I cross busy'd the channels using the busy ins and busy outs....which actually worked quite well..


Currently with the centracom setup, the dispatcher keeps their Select and unselect audio down and listens to comparator audio only on an external speaker... they select or instant transmit just like usual on the centracom and we force select a channel on the voter during a PTT situation and that channel has no audio on it, which prevents feedback from the other sites....which works quite well...

I dont have a pin/punch number with me....but i have tested this already and it works flawlessly....i read all of the info about main/standby in the installation manual for the 4000 series...

thanks,

nick

First Reponse:

Wow; you learn something every day.

There is indeed a pin on the channel cards (single pin: #3 for Chan. 1, #9 for Chan. B, #15 for Chan. C and #21 for Chan. D) that goes to ground when you program a button for "Main/Stby" and don't give it any other instructions. Right there in front of my face. I won't tell you how many times I've just used an output on the Aux I/O card for this function. Good thing we weren't running short of outputs!

Second response:

I think your proposal is sinking in: what you want to do is (a) normally listen to the Audio Out from the comparator (voted audio), but (b), on demand, be able to listen to the audio coming directly from any 1 of 11 receivers (which is the same as the audio coming IN to any 1 of 11 comparator receiver cards).

Yes, you can do that with relays, as I've suggested.

You can use your per-channel Aux Out to pull in the relays, but then you'll need 11 channels (6 DCCs) plus 11 relays. The relays are cheap, but the channel cards are close to $2K per, which means about 12K for channel cards.

I think you can achieve the result with only 1 channel card, as noted earlier. Wire Ch. 1 to comparator audio output. Wire Ch. 2 to the parallelled output of 11 relays, the input of which is a single receiver audio line, and the coil of which is pulled in by a "1 of n" set of Aux I/O (using the Aux I/O card) buttons. One of the Aux I/Os would do nothing, so that no relay is pulled in and Ch. 2 hears nothing. Ch. 2 would be set for RXO.

If I'm right about this, you'll save $10K.

However, I assume that your receivers are sending a SpectraTac 2175 status tone when squelched, and doesn't this mean that, however you end up accessing "direct" receiver audio lines, you are going to have to deal with hearing that tone, no?

Or have I missed the whole thing altogether.

Now, you have one other problem, which is unrelated to radio. The world of radio techs is divided into two groups of people: those who are open to (and occasionally even enthusiastic about) custom solutions to unusual problems and those who will never entertain anything other than the identical "by the book" application that they've used in the past 100 jobs. If, as I sense, you are encountering this sort of resistance, it is a problem that no one here can help you with.

KuhnElectronics wrote:Currently with the centracom setup, the dispatcher keeps their Select and unselect audio down and listens to comparator audio only on an external speaker... they select or instant transmit just like usual on the centracom and we force select a channel on the voter during a PTT situation and that channel has no audio on it, which prevents feedback from the other sites....which works quite well...

Nick,

Your ideas are awesome, don't let anyone else shoot them down.

I have a couple of comments though:

The above force-select of a channel on the voter with no audio is unnecessary. Centracom II and I would hope the Zetron would as well, has a cross-channel and acoustical mute option that will mute other channels when transmit is pressed...

So the force-select thing shouldn't be required - just program the console for cross-mute or acoustical mute. Research that.

Second off, I would suggest they upgrade that Doug Hall voter... Not a very solid product in my opinion, I think it was primarily designed for ham use (though I could be and probably am wrong, I'm just looking at the other products the company has produced...)

They seem AWFULLY scared of a voter failure... I think a new voter and some reassurance would really clear up a lot of this work for you...

Can I ask what the customer's function is? I've done work in some very major dispatch centers, and I've never encountered any requirements like this before...