Can anyone tell me how this works and does the disconnect come in many forms?

Also how would I tell or find out if an analog extension has or performs disconnect supervision?

Thanks for any help

If you hook up a volt ohm meter and read the DC voltage you will see it drop off from the 8 to 12 volts you're seeing on off hook battery and go back to 48 volts idle line voltage. You can also use the light on your toner. It will dim on a call than go out and come back bright on idle voltage. This is also called calling party control.

There are different types of disconnect supervision depending upon the line type. In most cases (and the most problematic), supervision on loop-start lines is what you will encounter. For a line or even a single-line station port to provide loop or disconnect supervision is for the line to go dead for about a half second when the calling party hangs up. When I say dead, I mean near-absence of line voltage. This "open loop" signals the equipment that the caller is gone and that it is OK to knock down the call, release a held line, voice mail port, etc.

The easiest way to test is to put a tone generator across the line or extension port, but leave it turned off. The continuity light will show that there is line voltage present. Make a call to that line and make sure that it is answered. Hang up from the calling end and watch the LED on the tone generator. It should go dark for about a half-second after the calling party hangs up. This may take up to 15 seconds or so to occur. If the LED never goes dark, then you are not receiving loop supervision.

Didn't see this. The diconnect supervison comes from the CO not the extension.

I like the hat Ed.

In some PBXs, disc. supervision is available on extensions. From other ext.s, c.o. line, or both. John C.

So if I had analog extensions that don't have disconnect supervision then how do the phones know when to hang up. If one side hangs up and the other stays off hook what triggers the release of the line?

My reason for asking is, I have to integrate with a confer III, conference bridge with analog extensions. From the confer III documentation the bridge needs a disconnect super and it only supports (Loop-current interrupt, Dial tone detection, Reorder tone detection, A-tone, D-tone) I don't think I have to worry about calls into the bridge from telco, because telco will send disconnect Super. But if someone uses a analog extension or a IP phone to call in locally to the bridge, I dont know if the bridge will get the proper disconnect it needs.

I appreciate your comments

What type of system are the analog extensions coming out of? As Lightning noted there are some systems that do provide it.


Ed
if we can all make it to the 10,000 posts will we also get one of them hats......I have a long way to go so I am not too worried yet.

Most PBXs and hybrid key systems give some sort of reorder or dial tone return. Heck, it's choosable on the Mitel SX50! John C.

Don't forget reverse battery.

This product has saved us --

https://www.vikingelectronics.com/products/view_product.php?pid=497

Disconnect Supervision came with CO lines then I started having problems a few years ago with hung lines, The local telco took it off lines then wanted a ridiculous one time fee to put it back on, the biggest assinine telco stunt i have seen, I wont mention telco name but it starts with sprin and now starts with embar!
Default on a DMS switch has it ON, these scumbags went thru and turned it off so they could rape their customers!
JUST WRONG!!

We have the same problem here. Embarq makes you pay $3.00 per line to have it with a $35.00 on time charge. When we sell a new system we have the phone company add it to their lines and explain to the customer that we are not doing this to them but the phone co.

Like Kevin says JUST WRONG!!!! :bang:


Cosmo

Not to be a curmudgeon - but isn't this why ground start was invented?

Some Voice Mail systems and Conference Bridges have always been problematic in their disconnect recognition and the gadget that Noisy Cow recommends seems like it would do the trick.

If people are having trouble with their Telephone Systems disconnecting properly is Ground Start no longer an available option for these systems?

Sam

Sam, quite a few systems simply don't offer ground start trunk ports. In the PBX world, loop start lines are rarely heard of, but in the key system world, it's the other way around. Or so it seems.

Justin

Justin -

I figured that, but I was wondering about all these hybrids. I seem to recall that the few I worked on back in the day would take them - sometimes it was a software option, you didn't even need a different card.

Sam

I think that the true benefit for ground-start trunks was to eliminate call collisions or "glare" where an outgoing call was attempted at precisely the same time that a call was coming in over the same trunk.

Supervision on loop trunks or even POTS lines has been the norm as long as I can remember, but that was long before the days of voice mail. The proverbial open loop just caused key system CO lines to release a hold condition when the call was abandoned.

Ed -

True. But true disconnect was also part of the equation. There used to be a thing called "Calling Party Disconnect" where if the calling party DIDN'T hang up then the call would stay up forever. Ground Start took care of things like that.

Sam