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New Member

Beyond the Butt Set: Troubleshooting Groundstart

I'm wondering if there is a more sophisticated way to test analog ground start lines than using a Butt Set? Last week we were setting up a CCME system with a VIC2-4FXO configured for ground start. The cabling contractor was able to get dial tone from his Butt Set, and the Telco (of course) swore there was nothing wrong with their end of the circuit, but we couldn't make any outbound calls (yes, we checked Tip/Ring polarity).

I saw the Cisco whitepaper on testing outbound ground start, it recommends using a multi-meter and oscilloscope. Are there any better (easier to use) tools out there? Maybe one of you old telecom guys can recommend something?

Thanks, Randy


Re: Beyond the Butt Set: Troubleshooting Groundstart


Been there, done that.

I have never seen VIC2-FXO ground start work with a DMS100 CO switch. A VIC-FXO or HDA works fine. Cisco says the VIC2 conforms to the spec, and the VIC does not. Too bad the CO techs aren't interested in reading Cisco white papers. I fought this for awhile, but finally just gave up, and put in older routers at the few sites where this was an issue. Or you could check to see what other disconnect supervision options the Telco can support (assuming that is why you chose ground start).


New Member

Re: Beyond the Butt Set: Troubleshooting Groundstart

This concerns me because in the not-so-distant future we're going to be putting out quite a few 2800 series routers with VIC2-FXO modules at sites that use a lot of ground start lines.

You seriously have never seen one work with the DMS 100? I'm pretty sure that that's the most common switch in our area. It sounds like you must have had a TAC case open. Were they not of much help?

New Member

Re: Beyond the Butt Set: Troubleshooting Groundstart

It appears that there is a known bug related to this, CSCee11089. It has been fixed, though. Have you verified that you are using the newer DSPware that has this fix?

New Member

Re: Beyond the Butt Set: Troubleshooting Groundstart

Did you verify that the router was grounded to the same ground that the telco provided for your lines?


Re: Beyond the Butt Set: Troubleshooting Groundstart

My experience was about a year ago, and may be out of date. I did follow the Troubleshooting Groundstart FXO Guide. It appears that this has been updated since, so perhaps the current DSP versions in the 2800 have resolved this issue. We did verify proper grounding, and also tried the groundstart auto-tip delay, which was no help.

I only needed 2 FXO ports and had 2620XMs available with VIC-2FXOs, so just replaced the 2801s, and called it a day.


Re: Beyond the Butt Set: Troubleshooting Groundstart

i had a similar issue with outbound calls not able to work. from what i could remember it worked for a day and then something went crazy. my reason for ground start was because of disconnection issues. however, my workaround was asking the telco to put the lines back to loop-start, put the lines in a trunkgroup and enable COD (this is all done from the carrier side). that along with some signaling parameters on the fxo port itself fixed my disconnection issues.

New Member

Re: Beyond the Butt Set: Troubleshooting Groundstart

Well, I thought I would let this thread stew for a bit then review the answers.

I appreciate the replies, but no one has answered my question yet. I need to find a way to quickly find out if a Ground Start line has been provisioned properly. For example, Fluke makes a Cat 5 cable tester that tells you if the cable pinout is correct, the cable length down to a few inches, cross talk, etc.

We did eventually get the CCME problem figured out. My problem is I will be doing another dozen of these installs this year, and I don't want to be spending hours with TAC for each one. In this case, converting to loop start is not an option.

Some of the thing I am considering testing are:

Loop Current

Ground continuity

Tip & Ring polarity

AC voltage

There are some PC based oscilloscopes & multi meters out there, it would be cool to have something I could connect via USB port and automatically run a series of tests to find out just how good that analog line really is.


New Member

Re: Beyond the Butt Set: Troubleshooting Groundstart

Others may disagree but I think that using a buttset is a really good test. If you can ground it and get dial tone then the line is probably working correctly. If the line doesn't work when attached to Cisco equipment then the problem is probably with the equipment, not the line.

I may change my opinion when I start rolling out ground start FXO ports with Cisco IPT in a couple of months. :-)

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