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Joined: Jul 2011
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Hey guys, got an issue I'm trying to sort out with Trunk to Trunk calls.
I've got a client who I've got a Trunk to trunk offsite setup for after hours where they put a CF to a cell phone on an Ext. So calls come in, hit the auto attendant, the press 0 for maintenance, it rings to Maint Ext with the Call Forward, grabs open trunk, dials the cell phone. However, once either party hangs up the call, the Lines stay lit and do not disconnect. You have to physically disconnect the line for the calls to drop.
I have plenty of clients who use this feature on SL2100's as well as our shop we use it on our SV9100 for emergency calls. The service coming in on the client side is grandstream and its using a break out from sip to analog. Now, I contacted the service provider and they say its the phone system end.
I have had no issues with Spectrum or ATT services with the analog co's, but I'm trying to figure if there's a trick that I'm missing or if grandstream is full of it. I had called Teleco which they stated is not a NEC issue. Thoughts?

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The Grandstream is probably not configured properly to provide CPC. I would guess that this is not an NEC issue.

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thats exactly what I've been saying. But now I have a feeling I'm going to have to program some sort of disconnect timers, which I'm totally against as I dont want it affecting every call being made, only if it's a trunk to trunk sent off by that single extension.

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Is there a reason that the Grandstream is in place? Can they just move to sip trunks on the 9100?

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https://support.ringlogix.com/index...dstream-gxw4216---disconnect-supervision

Clearly disconnect supervision is not on. Much better if you moved to SIP or PRI. NEC won't really help you because trunk to trunk is not something they recommend via analog.

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On another forum, there was a remarkably similar post, just not trunk to trunk. First, you want to make sure you are chasing the right goose. Connect a test set or single line phone to the ATA analog port. From your cell phone, establish a talk path to your ATA device. Hang up the cell phone and listen carefully to what happens on the phone connected to the ATA port. You should hear 2 distinct clicks if the device removes then reapplies current to the interface. This is a proper loop disconnect and will cause the NEC to drop the call on its side. If it goes to dial tone, busy tone, or silence, that is NOT a proper disconnect.

If you can get into the device look for settings on the analog interface relating to disconnect, loop reversal, calling party control, or other similar terms. This other poster dug around and figured out how to get it working.

I ripped this from the Grandstream support site and it might point you, or the service provider, in the right direction.

- Re-configure the GXW410x to reflect the disconnect signal used by the PSTN carrier.
- Power Disconnect: navigate to FXO Lines in the web configuration pages and set Enable Current Disconnect to “Yes”. Make sure the correct duration of power loss is set in Current Disconnect Threshold. Set Enable Tone Disconnect to “No”. If there is a parameter for the disconnect timer, start with 600ms. Give the NEC a good disconnect on the loop. Test again to familiarize yourself with what this sounds like and you can easily impress others with your knowledge lol...

As much as it would appear to be an NEC issue, it is not. The NEC requires loop disconnect to drop a loop start trunk when the far side hangs up. You actually WANT CPC from the ATA because calls to a voice mail box will not disconnect when they hang up after leaving a message either. You want to emulate wat the telco does as much as possible since this is what the equipment is manufactured to work with.

It is funny how this old school stuff is coming back around. I used to encounter this with answering machines in the late 80's and early 90's. Oh, the arguments with the customers and the conversations with the phone company. I learned that butt-set test quick and it cuts the time of arguing down to under a minute because you can simply demonstrate whether there is disconnect or not quickly.


Michael Meyer

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