Tuesday, February 7, 2012

Telephony Basics Pt 5

Okay, so now that we have a phone line interconnected from the PBX to the IDF(s) and then to the end user, how do we troubleshoot it if it doesn't work?  My methodology is to work from the MDF out.  I have two tools I use depending on which type of phone I am troubleshooting.

Butt Set
For an analog phone or fax, I use a traditional butt set.  A butt set is a ruggedized telephone handset with a set of clip leads that are used to clip on to a 66 block or other terminal.  Because the metal part of a 110 block is hidden, a special adapter has to be purchased to use a butt set with a 110 block.  If you don't have the adapter, you can remove the jumper and then use a spare piece of jumper wire to punch down to the block and then connect the jumper wires to the butt set clips.  At each step from the MDF out I will hook up the butt set and see if the line works.  Wherever it stops working helps me isolate the problem.  Generally for me it usually ends up being that I have a loose jumper wire, or I punched the jumper down on the wrong terminals.

If the line in question is a "digital" line, the standard butt set won't work.  What I do in that case is I take a RJ-45 jack and wire pins 4 and 5 to a jumper cable.  I then punch down the jumper cable to the points along the path and use the same model phone as the line is configured for to test the line.  It's a bit more cumbersome, but it gets the job done.

This concludes my series on basic telephony and I hope it has been useful to other router jockeys out there that have been put in the situation of learning telephony too.

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