sundance-communications.com/forum Forums Wiring - Telecom Carriers - Trunks & Services Telecom Service & Providers Ground start Loop

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