Telephone Radio Circuit Monitoring

[Gigs]

Hi. We are using a a telephone "special radio curcuit" through Sprint Phone Company. This "special curcuit" has NO Voltage what so ever on it and is only a pair of "copper" wires between communications and the tower site. (Tone Remote). I verified there is no voltage on the line, again tone remote type only It probably about a 3 mile run. At communications, it comes in on a "punch block" where a pair comes off and goes into the console equipment (Centracom Series II). It goes out of communications is has a "triangle" effect; it goes to the police station about 3 blocks away for a remote, and also goes to the tower site for the transmitter. The lines are "tied" together at the phone company just up the street from communications. Anyway, at the transmitter site is an MSR2000 UHF Repeater.
What I want to do is put something on the line at the transmitter (such as attaching to the punch block "in line" with the repeater out/in pair power of DC or something putting voltage on the line. At the other end (communications) at the punch block where the line comes off to goto the console. Something there like a relay or something this is constantly NC, but when the line would get open such as a vehicle accident into a pole, someone at the phone company accidently cuts the wrong wire, etc. the relay would Open and cause strobe or something at communications to flash stating there is a problem with the phone line. I'm thinking DC voltage of some sort and I obviously do not want it to interfer with the audio on the line for the transmitter or blow up the console or transmitter because of a voltage. Has anyone done something like this, and can any suggestions be made to accomplish this without affecting the audio or blowing something up. Also, I'm worried about the "loss" in voltage at the other end and what would be needed to ensure enough power gets to the other end. THANKS

[k4wtf]

Use DC and use capacitors to isolate the "hot" section of the line from your consoles and your repeater. Much like the "power injectors" used for tower-top RF preamps, etc.

Good idea by the way.

John

[jhooten]

Talk to Sprint before you do anything to the line. If you put anything on the line that causes damage to their equipment YOU, not the department, will be in deep doo doo. And even if they find you have modified the line, damage done or not, it may be grounds to cancel the contract. You will find that Telcos are very persnickity about their wires.

[nmfire10]

That can work ONLY if it is actual uninterupted copper from end to end. If it goes into a SLICK or has any other fancy phone company foot work, it will not work. Also remember, these things are not direct runs from one location to another. Everything begins at the phone company CO. So you have a line from the CO to dispatch, CO to the police, and CO to the transmitter. It is all tied together in there. You don't want to just start putting voltage on a copper pair before checking with the phone company to ensure your circuits can support that. These are only designed with AUDIO in mind so you need to confirm.

[Pj]

Exactly. A couple towns near me used some law that allows for municipal lines to be ran on utility poles without a fee. They ran all their radio/network and everything else in between on them so they would have full control.

[Dan562]

Gigs,

You haven't stated which version RT Telco Lines you are presently using, I.E. RT2002, RT3002 or T1. Each has it's on set of specifications. Secondly Sprint or any other Telco provider can and will not guarantee DC continuity Telco pairs between the console and the base station site. This is part of the reason Tone Remote Control TRC was developed 30 to 35 years ago.

I'm absolutely sure if you are using a 2 or 4 Wire Line (WL) circuit between the Centracom console and the remote base station. What might be an alternative idea to consider would be super imposing an audio frequency down the Telco WL from the base station using something like 1150 Hz @ -13 dBm as the Status Tone. The Status Tone would Mute each time the receiver would detect the carrier and proper decoded PL. Have a detector at each console and audio notch filter so the Status tone is not heard. In the detector circuit also provide a NPN transistor switch output to the console to indicate the loss of the WL Link.

You make check if the following Service Manual # 68-81114E57 is still available through AAD to use as a reference Spectra-TAC Encoder and a Spectra-TAC Comparator Manual # 69-81039E50 for the Status Tone detector circuit on the TRN6091C Signal Quality Module and the TRN6093A Command Module Audio Notch Filter circuit between Q9 and Q10.

I highly discourage you from using the standard 2175 Hz Status Tone on a 2 Wire Telco circuit between the Base Station and the Console because of the TRC Keying sequence HLGT 2175/FT 1950/LLGT2175 which the LLGT @ -30 dBm holds the transmitter keyed until the 2175 Hz tone is removed. If the console unkeyed and the standard Status tone instantaneously appeared, the transmitter would never unkey till the Time Out Timer killed the function. It would cause more headaches than help.

Dan

[Wowbagger]

Use a "subaudiable" tone, like a standard PL decoder.

This way, you don't need to assume the wires are a dry pair (telco parlance for bare copper that is not connected to system battery).

Use a standard PL detector - if it drops out, you've lost connectivity.

[Wile E. Coyote]

I agree that you should NOT use DC on this phone circuit. Most phone companies lately have been revamping their systems so that DC is not supported (unless grandfathered). If you did put DC on the line, it most likely will be filtered out at the central office and that is as far as it will go. Stick to the status tone that Dan562 mentioned and you will be fine

This reminds me of a time when Qwest cut a DC radio pair and accidently crossed it with a fax phone line. the ring voltage had enough kick to key the base and we could hear fax tones over the air. when we complained to qwest, they said they modified the circuis in that area to fiber. On top of that, they said they could not run DC through it (obviously). so much for DC!

[copcarguy]

Is " persnickity " A word?? What does a "persnickity" face look like?

Its in jhootens reply.

Just trying to put a smile on everyones face...lol

[Wowbagger]

http://dictionary.reference.com/search?q=persnickety

per·snick·e·ty
adj.

1.
1. Overparticular about trivial details; fastidious.
2. Snobbish; pretentious.
2. Requiring strict attention to detail; demanding: a persnickety job.

[xmo]

The ideal arrangement would be to have a 4-wire circuit.

You would send a pilot tone up from the console end to the base station end where it would be decoded. The decoder output would then turn on a second pilot tone which would be inserted into the receive side of the line and be decoded at the console end.

That would give you confirmation of line functionality in both directions.

Obviously you would notch out the pilot tones. Wowbaggers suggestion of PL tones could make the project fairly easy [off the shelf parts] assuming the line will pass the required low frequencies.

If you desided to use higher frequency tones - stay away from the S.F. signalling range or you might cause trouble on the circuit - some of the telco line cards use these frequencies to set up loop back testing.

[OX]

Putting voltage onto that circuit would for sure cause problems with the Telco's equipment at the CO. Those circuits are designed for audio only and there is amplification in-between. Telco's can get really pissy when you start messing with their lines. You can use the suggestions above but maybe you should check with Sprint about two items:
1) Line fail detection schemes on the existing circuit.
2) Backup lines when/if it goes down

Also, how much DC power were you going to send over that pair to travel 3 miles AND pull in a relay coil? I figured a voltage drop of 2.2V/100' of 24g wire, over three miles yields a hefty 350ish voltage drop.

I'd go with microwave remotes and ditch the copper pair.

[moto]

I run a communications center with 40 RPTA radio circuits. The phone company will not allow you to put anything on the lines. If you do, anytime the circuit goes bad they are going to say its your equipment causing the problem. When you lose a circuit you'll know right away because you wont be able to TX or RX. Even if you knew instantly they are still not going to fix it as fast as you want. (And we in the business want the circuit fixed like yesterday when they go down).

Good luck!

[nmfire10]

Actually, to be more accurate, when you call them, they will first send a technician to break it even more and cause a whole new set of problems. Then they will resubmit it as a problem requiring a higher level tech. This will go on for about 4 days minimum. After those 4 days, they will realize the only reason it doesn't work is because some moron pulled the clips on it in the CO because "he didn't hear anything on the line so he thought it was not in use."

Then they will fix it and bill you for it.

[ricciticcitembo]

Actually, to be more accurate, when you call them, they will first send a technician to break it even more and cause a whole new set of problems. Then they will resubmit it as a problem requiring a higher level tech. This will go on for about 4 days minimum. After those 4 days, they will realize the only reason it doesn't work is because some moron pulled the clips on it in the CO because "he didn't hear anything on the line so he thought it was not in use."

Then they will fix it and bill you for it.

Yup. Got that right.

[chipjumper]

Microwave remotes? How much are we talkin here slim?

[OX]

Not sure, never priced them personally. But it's gotta be cheaper than paying that big lease line charge to the Telco for years and being at THEIR mercy. Being a high priority subscriber costs more too.

The PMNA circuits used to run upwards of $100 a month from point to CO to point. But this one has an extra branch so figure more.

[Jim202]

I would doubt that you could get a "PL" tone to tavel over a standard telephone audio circuit today. They line amps used on the circuits today are not designed to pass that low of a audio frequency. Todays line amps have the roll off designed to go from between 300 and 3000 hertz. The "PL" tones don't go that high. You might luck out and get something to get through, but I wouldn't expect the line levels to be much to work with.

Back in the days when you could get a metalic pair from one end to the other, this was a different issue. However again, there was generally a loading coil or several on the cable circuit that made the low and high tones hard to pass.

Jim

[ANB_Medic]

Actually, to be more accurate, when you call them, they will first send a technician to break it even more and cause a whole new set of problems. Then they will resubmit it as a problem requiring a higher level tech. This will go on for about 4 days minimum. After those 4 days, they will realize the only reason it doesn't work is because some moron pulled the clips on it in the CO because "he didn't hear anything on the line so he thought it was not in use."

Then they will fix it and bill you for it.

What telco do YOU use??

Todd

[bjlf]

Please do not induce any volage onto a telco pair.
If you report trouble I'm gonna look at the line see voltage one direction or another this will make testing more difficult.

Are these normally open or closed.

Yes it will take longer to fix.

I work for a local telco, volunteer for the local FD and take care of some of the radio's.

Just becuse it is only 3 miles, driving i asume, does not mean it is 3 mile cale distance. there may be telco equipment that the added dc could harm, that will only make me less cooperative.

It is problematice if the pair goes open, but if it is an accident or strom that cuases this it would be one of my first prioraties to keep working,

[N9LLO]

Sounds like you have what they call an "unconditioned pair" or true DC circuit. I actually got one of these setup with SBC a couple of years ago
and we ran one of those video modems across it to setup a remote security camera at a site across town.

I think it helped that we have 2 full time SBC techs stationed at our plant but it still took some doing to get it ordered.

Chris
N9LLO

[kb4mdz]

Actually, to be more accurate, when you call them, they will first send a technician to break it even more and cause a whole new set of problems. Then they will resubmit it as a problem requiring a higher level tech. This will go on for about 4 days minimum. After those 4 days, they will realize the only reason it doesn't work is because some moron pulled the clips on it in the CO because "he didn't hear anything on the line so he thought it was not in use."

Then they will fix it and bill you for it.

What telco do YOU use??

Todd

Just the standard only-game-in-town, close-the-ticket-without-doing-jack, gotta-keep-my-ticket-percentages-up-to-get-the-bonus-I-don't-deserve, yadda, yadda, yadda.

Oh, and by the way, just because it's a public safety customer doesn't mean they're gonna be any kind of fast on getting to it, especially on a cold, rainy, weekend nite...

Other than that, I love my local telco. (gee, there's no emoticon for a 'smirk, and a snort thru the nose').

Chuk

[n5tbu]

Around here it's a Bellsouth line,and if it goes down,they test it in New Orleans or Shrevport,then they say it is working! Then I say send out a tech from Dmark to Dmark.....then they say it works! 2 days later when the tech actually calls me direct because he is LOST....then after I explain how a radio circuit works vs a phone circuit.....then he gets it fixed!
Thats a tone problem....now ,a dc line? good luck!
mod

[kf4sqb]

Y'all think you have problems? Our main radio is tone remote over a leased line also. However, ours runs through TWO different telcos. Double the fees, and when something breaks, the two telcos will spend at least a day pointing fingers at each other and saying "it's not our problem, it's on their part of the line". We are seriously looking at the possibility of switching to a Canopy system and getting rid of the leased line alltogether. Our main problem with Canopy is the distance.

[thebigphish]

Actually, to be more accurate, when you call them, they will first send a technician to break it even more and cause a whole new set of problems. Then they will resubmit it as a problem requiring a higher level tech. This will go on for about 4 days minimum. After those 4 days, they will realize the only reason it doesn't work is because some moron pulled the clips on it in the CO because "he didn't hear anything on the line so he thought it was not in use."

Then they will fix it and bill you for it.

What telco do YOU use??

Todd

matt, u stuck with sbc down there?

[nmfire10]

Unfortunately, yes. It took them 7 days to move a service entrance from one side of our building to the other... and the CO is ACROSS THE STREET!!!!!

[raymond345]

well in canada we have used telco leased
lines for over thirty years with very minor
problems.A lot of the lines are direct and never
go through the main C.O.

It depends what the line is used for.

1:we use the 1000Hz tone to test for service.

2:Resistance was a second test on some of the
lines.

It is very fast to see who is at Fault when a LINE
FAILS.

Before competition came along We had a bit
time to repair a line but now it is no big deal.

We never had to fight too long to get service.

.

[Bob W]

Putting voltage onto that circuit would for sure cause problems with the Telco's equipment at the CO. Those circuits are designed for audio only and there is amplification in-between. Telco's can get really pissy when you start messing with their lines. You can use the suggestions above but maybe you should check with Sprint about two items:
1) Line fail detection schemes on the existing circuit.
2) Backup lines when/if it goes down

Also, how much DC power were you going to send over that pair to travel 3 miles AND pull in a relay coil? I figured a voltage drop of 2.2V/100' of 24g wire, over three miles yields a hefty 350ish voltage drop.

I'd go with microwave remotes and ditch the copper pair.

That would be correct if you were trying to use a relay that needed a 1/2 amp (actually 441 ma) to pull in. Now, as far as putting DC on the pair - if there really is DC continuity between all three locations - which means that there's no SLCs, etc. You CAN put dc on the pair (if you have direct access to it - see below) without upsetting TELCO. It needs to be current limited to less than 40 ma, and it has to be less than 52 volts. That will drive 26,000 feet of 24 gauge cable. If the source is well balanced -tip to ring, which means no ground hum - telco will think nothing of it. One way to do this is to provide a DST that is capable of providing sealing current at the radio end. You'll need to provide a means of detecting the existence of of the current at both tone remote locations. The problem here is the telco may already have DST's at all ends which means that you do not have dc continuity to the pair. The right way is to use a status tone from the base station.

[SheriffDspatchr]

Actually, to be more accurate, when you call them, they will first send a technician to break it even more and cause a whole new set of problems. Then they will resubmit it as a problem requiring a higher level tech. This will go on for about 4 days minimum. After those 4 days, they will realize the only reason it doesn't work is because some moron pulled the clips on it in the CO because "he didn't hear anything on the line so he thought it was not in use."

Then they will fix it and bill you for it.

Sad but so very true, does anyone else have this same type of frustration (on a daily basis) with these types of radio circuits ? I just spent the better part of 10 days playing this same game with these people only to have them change out the package just to get the circuit working, not to mention all the headaches it took to balance the line levels and finally get the circuit to work ! I'm curious to see how other agencies (perhaps in Massachusetts) deal with this type of unacceptable service.

Scott

[mastr]

Scott-

I have been dealing with Telco people for the past 30 years. The first thing you have to realize is that even when the Telco is wrong, they are right. In other words, most of them have no mechanism in place to say, "we were wrong, that caused you to waste lots of time, so here is a sack full of twenties for your trouble."

One of the best things you can do is develop a working relationship with a couple of techs and perhaps a field supervisor in your area. Go to them when you have trouble, and have your trouble report "translated" in to something that the rest of the telephone company will understand. It is often amazing what a well-placed call from the right telco supervisor can do.

[GMC]

Hello,

Back when I was doing this on a regular basic (haven't in about 4 years), the telco (ny telephone, nynex, bell atlantic or what ever they are being called at the moment). had a "specials" department with a 7 digit phone number. Since this is all they did they had a very good understanding about these circuits. They were usually repaired within 24 hours. We were also able to have certain circuits tagged as requiring immediate attention, and would be repaired within 2 hours.

Gary

[Jim202]

I would suggest that you try and have a mmeting with the account rep for your service. Have a good sit down discussion on the problems and issues your having troubles with. Find out just what kind of a service responce has been assigned to your circuits.

Then when you have a problem, make the call to the service number. Wait the number of hours given for service restoration. If it is still broke, call the service number again. Only this time insist that a SUBSEQUENT TROUBLE REPORT be subbmitted. Also ask that the problem be ESCALATED. Ask to speek with a supervisor and insist that you be connected with one and not have a return call.

Don't forget to get the name or operator number of the person each time you get to speak with someone. It seems to make them have a slightly more of a responce to you when they know that you have their name or operator number. Be polite, but firm. Explain that this is a public safety circuit and that you expect the telephone company to treat the trouble call accordinly.

The bottom line is most of the phone companies have the managers pay review based on the completion and number of trouble calls placed. If you keep calling up every couple of hours and insist on another "subsequent trouble report" being filed, this shows up as another trouble report and not just a continuation of the original one. The black marks will pile up against the responsible manager in just a short time.

Someone will call you back along the way and want you to stop having trouble reports entered in. They will get the point and cry "Unckle" at some point. Make sure you get the name and a call back phone number of who called you. Ask what their title is.

Hope this gives you some pointers on how to handle a non responsive phone service problem.

Jim

[Gigs]

I've been following along with the posts regarding this topic. Just as an update, I do have a good "bond" with the 3 techs who handle this at the local CO. I asked them about line monitoring and they said it "straight-through" and they don't monitor it. They mentioned we would need to put something on the line for monitoring on our end. They were very positive that we could do something (put something on the line). Again, the problem is I don't know what that wouldn't affect the audio, etc for the repeater. One person mentioned putting a tone on the line, that would work in theroy, but that tone would be heard on the console end because its an "open" line to communications. The only tone is the "keyup" tone, otherwise the line is open for rx. We also use DPL and need to be careful that isn't going to affect the system either.

[nmfire10]

Well, it sounds like it is point-to-point dry copper without even going through the CO at all. Interesting. If that is the case, you can always setup a quasi status tone similar to what is used for voting receivers. You just need to notch out the tone frequency on both ends of the circuit. If the tone disappears or is fluctuating, you know the line is screwed.

[RADIOMAN2002]

I don't know if they are still available, but I bought some dc to tone remote interfaces. That is depending on the current sent out -15ma or + 15 ma or any of the other current levels, the converter board would send out a tone sequence 2175-1950 LLV 2175 The board was programmable,and could be used with the most common tone frequencies on remote radio systems.

[richyradio]

if they still allow dc on the line, (which I find rather amazing) rig it up just like the big M used to do it- you'll need a transformer with "split windings" on them- basically, each side that connects to the phone line is not a single 600 ohm coil, but (2) 300 ohm coils.....if you can visualize this, (not sure how much fiddling w/ electronics you do) the "ends" of each coil go to the phone line, and the other 2 go to: 1) a capacitor to complete the audio path, and 2) a relay that you wish to energize....the other side of the xfmr (which can be a plain 600 ohm non split winding) simply goes to the centracom junk...at the site end, you'll need a current generator where the relay was at the other end...doing it this way keeps everything balanced and the dc on the line should be invisible compared to ground...I.E. go out and get an official dc remote setup as you will need alot more than say, 12 volts to drive the line and you'll get everything in one neat package.....tell you the truth though, the whole dc thing I would not feel comfortable with...(think this falls under the category of the more stuff there is, the more stuff there is to go wrong)