When testing a ground start loop with a Butt Set, i put one lead on the ground, but does the other lead have to be on Tip or Ring, or does it matter. thanks

Put one lead on Tip and one on Ring and use a Ground to start the line.

for the ground you can run a piece of cross connect to a ground , strip the end and touch it to your buttset lead

so I clamp my two leads on the tip(green) and ring(red)as usual and touch any lead with a cross connect wire to ground?

A brief ground on the tip is the proper way. With the butt set off hook of course. Also just in case you weren't aware, GS trunks won't work if tip and ring are reversed.

Bill if the butt set is off hook you are grounding both the tip and the ring. a better best way is to leave the butt set on monitor touch what should be the tip, if you hear DT then go off hook and see if it holds DT; if you don't hear DT try grounding the other wire ( indicates the line is reversed).

That's a good point. I check for polarity first thing.

Edit my post above " touch what should be the tip" should read "touch what should be the ring"

Ground-start requires that both sides participate in a kind of "handshake". Think of it as a tiny, but extra step that your phone system has to make before a call can be placed or received. This handshake eliminates the possiblity of an inbound/outbound call collision or "glare".

Here's how it works: Your PBX looks for ground on tip; the CO looks for ground on ring. The absence of ground on the monitored lead assures each side that the other end is idle.

The PBX requests service from the CO by placing ground on the ring side. The CO detects this and responds by grounding the tip side. Your PBX sees this and says, "Oh good. He says that it's OK to place a call." The PBX then removes the ground on ring and closes the loop (user hears dialtone).

The near opposite happens during a CO-initiated seizure of the line. The difference is that the CO doesn't look for dialtone, but instead imposes ringing current across RING.

Taking a two wire butt set offhook by itself will NOT ground both tip and ring. However, unless you isolate the circuit from the PBX, you may find that you can draw dialtone by placing a ground across either tip OR ring (ground on tip looks like a CO initiated call; ground on ring looks like the PBX wants to place a call). My advice (and Jim's, I believe) then is to lift the bridge clips--or whatever--and take the PBX out of the picture before testing.

Bill simplified the whole thing by suggesting to first check polarity. If all is right with the world and this circuit, CO battery will appear on the ring lead (PBX side) when the circuit is idle.

thank you guys, this is a great website

One more question, I have a Harris TS22AL set, and I noticed they sell a p3218-441 ground start cord for this set. Now, I shouldn't need this right? Example: If the CO dropped a white blue/blue pair, my normal butt set would be the red lead (negative) connected to the blue(ring) and the black lead will touch ground to initiate dial tone. So I shouldn't need the cord, right? thanks again

How many ground start lines do you do?

By the way we in this trade use white/blue-blue/white unlike CAT5.

And it doesn't matter how you have your butt set connected as long as you momentarily ground the tip.

-Hal

Hal if you look at Rain's profile he's an electrician; how many GS lines would he work on?

I know and that was my point! I don't even have a ground start cord.

-Hal

"I noticed they sell a p3218-441 ground start cord for this set"

Just another $%^@#* cord to get snarled! But where in the world are Telcos still installing ground start? I haven't run across one in years!

I brought this up a couple of years ago. I don't think I got a good answer (or maybe I did and forgot it [would someone please call the old folks home and make a reservation for me?]).

But anyway - Are the systems going in these days not using groundstart? Is glare and the associated problems with 3-party conferencing no longer a problem? Is it by choice or do the systems no longer support it?

I'm also going to assume that no one uses metallic E&M trunks anymore - but please feel free to correct me.

Sam

I moved this here as it's a better fit, especially if were going to get into the whys of GS trunks.

One I don't work on the larger systems and only have one location with GS trunks which is a fair sized motel.

I don't think the reason for GS trunks has changed it was to reduce the number of needed trunks by using two way trunks with GS to prevent glare. Glare was and probably still is an issue. On GS trunks the loops are open when idle so unless you dial to hit it for outgoing or an incoming call is ringing in the loop is open. Both the PBX and CO get an immediate indication when the loop is closed due to ringing or hitting an outgoing line at the PBX, preventing glare. On a loop start line there is a lag between the incoming ring and when the PBX or KSU see's it. So if you hit an outside line during that lag time you will land on the incoming call ie glare.

Hope that all made a little sense.

Where ever it's being ordered... I don't see too many GS services ordered either but at least for now, Telco equipment can still support GS.


E&M? Eeeee-yeah... I don’t see anything NEW ordered with E&M signaling anymore… And to be honest, even though it’s still a valid signaling option by the tariffs, I have not seen any gear that can support it in a long time. :shrug:

When we put in the Saks 5th Avenue Headquarters (Neax 22L. I think the install date must have been 1982 or so) we had hundreds and hundreds of 4W E&M trunks - all on copper. When I was at the Bank of NY (1986) we still had 4W E&M - but they were all on T-1s.

Matter of fact most of the Voice (PBX) T-1s I put in for years used 4W E&M as the signalling method.


Getting back to Ground Start, besides glare we used to have a real problem with Loop Start circuits on 3 party conference - if one of the parties hung up the other two people fouind themselves conferenced in with "If you'd like to make a call, please hang up the phone".

Have the new systems managed to address these issues, or are customers just ignoring these problems?


Sam

T1E&M Wink is still quite common. Most installs I've worked are either that or ISDN.

I understand the superiority of ground start vs loop start. I also understand 2-wire and 4-wire metallic E&M and analog DID trunks. What I don't understand is where are telcos still installing analog trunks today? (and I do mean trunks and not lines). since the 90s, I have installed very few analog trunks. A few analog DIDs maybe, and an occasional E&M but is anyone still ordering and installing them in the 21st century? The only reason I can see the value of requesting an analog trunk today is when a loop start line is experiencing problems that the TelCo says is within normal specs. Requesting an upgrade to trunk status is supposed to make the TelCo actually qualify the line to ensure the best possible delivery of the trunk. (I think Mike Sandman has even referred to that last part as a solution as to when a subscriber has audio problems).

Sam, I think you may have said earlier that some schools in your neck of the woods are still using them? And if so, why? Unless there is a grandfathered price advantage, it just isn't sinking in for me. Do any of us still have pbx customers with equipment so old that they only work with analog trunks? I don't.

Dave -

Here in NYC, many years ago I discovered that NY Tel would sell you a GS Trunk but actually only deliver a GS Line. It had the opportunity of developing into a major scandal and class-action law suit, but politics squashed it,

I was curious if small systems (people that needed less then the 24 trunks a T-1 would deliver) still used GSTs. Admittedly my experience is ancient, but back in the day when I installed key systems and small PBXs, almost all of them had less then 24 CO circuits.

Sam

Old thread, I know, but I had to chime in.

My employer's Option 11 is still using ground start trunks. We also recently added more trunks and the CLEC had no problem hooking up more ground start trunks. We are now up to 23 trunks for the Option 11. Our vendor suggested that we look into a PRI to possibly save some money. I called our CLEC and their response was "What's a PRI?", so we still have GSTs.

Also, all of our trunks are used both for incoming and outgoing calls, so I would not want them to be loop start. Glare could potentially be an issue.

I have talked to a few techs, both with our CLEC and AT&T. They all have no problem selling and servicing GSTs. At least where I live, GST is still the standard for PBXs.

As a side note, once in a while we have to call for service on one of our lines. About half the time, the CLEC will fix the problem but also convert the line to loop start. I always have to call them back to get the problem solved. The worst case was when the LEC (Ameritech at the time) decided to move many of our lines into a PairGain because they were running out of space. It took AT&T, the CLEC, and our department weeks to get the problem fixed. The CLEC didn't realize that you can't run GST through the PairGain and Ameritech didn't realize (or didn't care) we had ground start trunks!

-Nelson

Thanks for chiming in, even on an older post...

I’m sure a lot of us have felt that pain when dealing with GS circuits and doing cut-overs to them… And that’s from BOTH side of the demarc.

I do need to mention though... Pair gain systems DO, do ground start lines. Not every voice channel card is capable of GS, but I have never run across any pair gain system that didn’t have channel cards that could be optioned for GS.

I do need to mention though... Pair gain systems DO, do ground start lines. Not every voice channel card is capable of GS, but I have never run across any pair gain system that didn’t have channel cards that could be optioned for GS.

Good to know, thanks Bryan. Since so many people have gotten rid of their phone line in favor of cellular recently, the phone company doesn't seem to be so concerned about running out of space as they were a few years ago. So, they have since moved all our GSTs back off the PairGain.

After they moved our trunks off the pair gain, they then moved our loop start alarm lines onto the pair gain. We then started having problems with our alarms. The alarm company kept calling us complaining of communication errors about three times a week. Again, the CLEC, SBC, and our alarm company went 'round and 'round about where the problem was. SBC kept replacing cards in the pair gain. Finally, they moved all our lines back off the pair gain and everyone was happy again. We've had no trouble since.

-Nelson

The next time someone doesn't know what a PRI is; say to them that it's ISDN.

With T1 service, Ground Start trunks are not as common today as they once were. GS was often requested when a D4 channelbank (such as a Newbridge 3624) was needed to interface the T1 to a telephone system that did not have a T1 card. Today the most common form of inband trunk signaling is T1E&M Wink.

Loop Start trunks on a T1 circuit are bad news for incoming calls. If an auto attendant is involved and the caller hangs up during the greeting, the system may not see a disconnect from the CO which can result in phantom ringing.

I was always told ISDN equaled "IT STILL DOES NOTHING"

Jim, I too had heard it in a similar phrase....when asked what ISDN was all about the answer was "I Still Don't kNow".....

:shrug:

GS, PRI, E&M, Wink they're really all the same principle. The signalling controls the circuit, not the loop controls the circuit.