[cisco-voip] Old cisco-voip thread on VG-224 dead ports

[Lelio Fulgenzi]

Thanks for sending this out Tim. I have been meaning to reply to it and am now just getting to it. 

We're looking at replacing a few VG248s (EOL) and our legacy PBX with VG224s and some VIC3-2FXS-E/DID if required. The differences between the three devices is interesting: 


Model 
	DID Loop Resistance 
	FXS Loop Resistance 
	Loop Length 

VG248 
	N/A 	415 ohms (on-premise only) 	5000 feet 
VG224 
	N/A 
	

Up to 600 ohm (including the phone or terminal equipment) 	



3000 ft, 26 AWG 
VIC3-2FXS-E/DID 	

Up to 1800 ohms (including terminal equipment) 	

Up to 1400 ohms (including phone or terminal equipment) 	

Up to 11,000 feet (3.3 KM) 24 AWG Category 5 twisted pair cable 


I'm guessing the loop length provided is simply an estimate, since gauge (AWG) and number of splice points affects this sort of stuff and we really should be trying to match the FXS loop resistance to ensure we're falling in spec and can call for support accordingly. I'd rather not use any extra equipment installed in between if I can avoid it. 

Anyone know what tools you can use to accurately measure the loop resistance? We're basically going to go to each circuit we have and decide if it falls within the VG224 specs or not since a 2911 with 4x VIC3-2FXS-E/DID has a port cost of about 4x that of a VG224. 
--- 
Lelio Fulgenzi, B.A. 
Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1 
(519) 824-4120 x56354 (519) 767-1060 FAX (ANNU) 
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 
Cooking with unix is easy. You just sed it and forget it. 
- LFJ (with apologies to Mr. Popeil) 


----- Original Message -----
From: "Tim Reimers" <treimers at ashevillenc.gov> 
To: cisco-voip at puck.nether.net 
Sent: Saturday, October 22, 2011 6:18:10 PM 
Subject: [cisco-voip] Old cisco-voip thread on VG-224 dead ports 



I was looking around for some info 
on VG-224 ports, and found this archived thread on Gossamer from 2008.. 

http://www.gossamer-threads.com/lists/cisco/nsp/96100 

I have a bit of info to offer on this one - although it doesn't help my problems. 

An old tip-and-ring PBX tech told me that in his experience, you can often get this behaviour from devices (ports, station extensions, etc in his world) when the line length is too long, and the impedance is very out of range. 

He says that can make ports behave badly and do this kind of thing, or blow outright from trying to match the impedance of the line. 

There are devices that can present the needed 600 ohm impedance to the VG-224 and stabilize this - 
Unfortunately, I am not enough of a line tech to know whether I'm seeing the right thing or not - maybe someone else knows of such a product by the correct part number from some manufacturer.. 

This makes for some interesting reading -- 
http://www.sandman.com/loop.html 
although it's pretty simple and sales oriented.. 



I have a VG-224 with some blown ports, but I can't find anything on VG-224 port repair, other than sending it to Cisco.. 





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