Leased Line Testing

[KE9GK]

Hello Board,

I have a (dumb) question for all of you with TELCO experience. I am looking at adding a spectratac voter and satelite receiver to my commercial repeater as I just discovered there is a punch block full of abandoned (possibly still active) leased lines between the main site and where I would like to put the remote receiver. This is an old abandoned VHF public safety setup.....and YES I have permission to do all of this with the owners of the sites -- so that is not an issue.

My question, what is the cheapest and easiest way to test the pairs for connectivity? I do not think these lines are "copper" pairs (although they may be) as there was never any DC control b/w the sites or console...only voice grade audio. I would like to map and correctly label the lines at both punch blocks. I would also like to be able to monitor the audio from the console to the base and vice versa on the line....can that be achieved by a simple lineman's test set and some banana clips on the right pair? Does the test set amplify the line audio so it can be heard...or is that another specialty tool I need? I understand how the lines work with the tone control etc....I guess I am just looking for some experts to verify my testing procedure and the necessary tools to accomplish the job w/o hooking up a console and tone remote base station to each pair.

Thanks

[Jim202]

Hello Board,

I have a (dumb) question for all of you with TELCO experience. I am looking at adding a spectratac voter and satelite receiver to my commercial repeater as I just discovered there is a punch block full of abandoned (possibly still active) leased lines between the main site and where I would like to put the remote receiver. This is an old abandoned VHF public safety setup.....and YES I have permission to do all of this with the owners of the sites -- so that is not an issue.

My question, what is the cheapest and easiest way to test the pairs for connectivity? I do not think these lines are "copper" pairs (although they may be) as there was never any DC control b/w the sites or console...only voice grade audio. I would like to map and correctly label the lines at both punch blocks. I would also like to be able to monitor the audio from the console to the base and vice versa on the line....can that be achieved by a simple lineman's test set and some banana clips on the right pair? Does the test set amplify the line audio so it can be heard...or is that another specialty tool I need? I understand how the lines work with the tone control etc....I guess I am just looking for some experts to verify my testing procedure and the necessary tools to accomplish the job w/o hooking up a console and tone remote base station to each pair.

Thanks

The simple way would be to put a TIMS unit on the cable pair at one end with a 1 KHz tone at 0 db and go searching for the tone at the other end. May not be the fastest way, but it will enable you to try and identify a working pair. It would help to have a second TIMS unit at the other end to measure the line loss if you do find an active pair. What ever you do, do not leave one of those line finder sending units on a line for more than a few minutes. They send well over the allowed level on the telephone pair and can cause all sorts of cross talk issues during their use.

You could go stir up a hornets nest and try to identify the cable number and pair. Then find a friendly local telephone service person to try and spend a few minutes with you on obtaining the circuit number associated with that cable pair. It takes a bit of arm twisting and cooperation from the local phone company, but it can be done. It may stir up some red flags as to why your asking and even if the circuits are still active. It is not wise to just stick equipment onto unknown cable pairs and start sending tones over them randomly. You never know what may come out of the woodwork.

Jim

[Bill_G]

+1 to what Jim said.

This would be easiest done with help. A person at each end would make the work go much quicker. If these truely are abandoned lines, and they have been abandoned for a long time, it is doubtful any of them are still built through. But, you might get lucky. However, you would at some point have to call the telco to tell them your intentions, or risk theft of service issues.

If you can get help, start with a simple fox and hound. Your helper puts the locate tone on each pair, and you look for it on the term blocks. As you confirm working pairs, you can try to find the telco IDs on the 21X blocks so you can transfer billing to your account. Then you can break out your TMS to measure loss and noise in each circuit you find alive. The line with the best results is the one you want to talk to the phone co about.

[wa6ylb]

Hello Board,

I have a (dumb) question for all of you with TELCO experience. I am looking at adding a spectratac voter and satelite receiver to my commercial repeater as I just discovered there is a punch block full of abandoned (possibly still active) leased lines between the main site and where I would like to put the remote receiver. This is an old abandoned VHF public safety setup.....and YES I have permission to do all of this with the owners of the sites -- so that is not an issue.

My question, what is the cheapest and easiest way to test the pairs for connectivity? I do not think these lines are "copper" pairs (although they may be) as there was never any DC control b/w the sites or console...only voice grade audio. I would like to map and correctly label the lines at both punch blocks. I would also like to be able to monitor the audio from the console to the base and vice versa on the line....can that be achieved by a simple lineman's test set and some banana clips on the right pair? Does the test set amplify the line audio so it can be heard...or is that another specialty tool I need? I understand how the lines work with the tone control etc....I guess I am just looking for some experts to verify my testing procedure and the necessary tools to accomplish the job w/o hooking up a console and tone remote base station to each pair.

Thanks

The simple way would be to put a TIMS unit on the cable pair at one end with a 1 KHz tone at 0 db and go searching for the tone at the other end. May not be the fastest way, but it will enable you to try and identify a working pair. It would help to have a second TIMS unit at the other end to measure the line loss if you do find an active pair. What ever you do, do not leave one of those line finder sending units on a line for more than a few minutes. They send well over the allowed level on the telephone pair and can cause all sorts of cross talk issues during their use.

You could go stir up a hornets nest and try to identify the cable number and pair. Then find a friendly local telephone service person to try and spend a few minutes with you on obtaining the circuit number associated with that cable pair. It takes a bit of arm twisting and cooperation from the local phone company, but it can be done. It may stir up some red flags as to why your asking and even if the circuits are still active. It is not wise to just stick equipment onto unknown cable pairs and start sending tones over them randomly. You never know what may come out of the woodwork.

Jim

I agree with Jim about the line level at 0 DBm, as that is pretty hot (by 13 DBm!). The maximum continous tone you'd ever want to present onto a leased line (copper or non-metallic) is -13 DBm. This represents the maximum level on a pair of lines. This holds true for standard voice telco lines too. I have even measured a typical land line modem and found its output level at -13DBm level too.
I remember years ago, a ham in the local area leased a local telco line to connect a remote receiver site to the main transmitter site for a repeater. He didn't know about the limitation on the leased line level and came home from work one day to discover his line was disconnected from end to end. Apparently, the level this fellow was running was causing all kinds of havoc at Ma Bell, and they "fixed" it by cutting his circuit! He since turned the levels down, and after much pleading with the local Telco, they reconnected the lease line.

B.

[Rod Farva]

on another note, check to see if the leased lines are 10db conditioned lines. The ones I currently work on are conditioned so when i send a 0db signal with my tims I should see a minus 10 at the other end and if the lines are conditioned and balanced properly by the phone company you should see a pretty steady level from 300 to 3000hz. There will be roll off below 300 and after 3000hz.

When you sweep the lines with the tims sweep them in steps of 100, starting at 104hz and ending at 3404hz. This way you should see the roll off prior to 300 and after 3000hz, and most of the time the phone company is too lazy to properly balance the card at the central office and you will see drastic changes in signal level as you sweep the lines. SWEEPING THE LINES IS VERY IMPORTANT. Not having a balanced line will seriously affect your audio quality.

Once again if your going to use a leased line you will be better off sweeping the lines first with the tims and having 10db conditioned lines. I would have the phone company balance the line and make sure your not double terminated on your tims when running 2 sets while sweeping. Being double terminated will affect your reading.... Sorry for jumbling my information, I am on my phone