Telecommunications Tech Blog April 2013
The Value of Call Accounting (CDR) / Station Message Detail Recording (SMDR)
in Fixing Strange Phone Problems on Phone Systems
By Mike Sandman •
You don't know what you don't know... BUT sometimes you
can find out with SMDR / Call Accounting!
An Interconnect (phone system vendor) sold a new phone system to a company for
$12,000. His customer ended up spending another $3,000 in T&M labor as he tried
to fix a very strange problem.
A phone would ring on the new system and a user would answer “Hi, this is Joe.”
The person on the other end of the call would say “Hi, this is Bill.” They would
both say “How can I help you?” The call would go on that way for a while, since
both of these people answered their phones that had just rung. They both were at
that same company.
It was happening to different people at the company, a couple of times a day.
The new phone system was blamed, so the Interconnect changed out all of the
trunk cards to try to track down the problem. The owner of the company wasn't
happy. The Interconnect didn't want to have to take the system out and give the
guy his money back.
The problem never went away, so the Interconnect decided to put a PC with
Hyperterminal on the SMDR port for a while and take a look at the raw data.
After a couple of days he found the same pattern of calls - a couple of times a
An employee was calling the main number at the company from his extension, and
entering an extension for another employee into the Auto Attendant. Then he'd
transfer the call he just made to some other employee in the company, and
hang-up right away. It seemed to everybody like the phone system was randomly
making calls between extensions.
The Interconnect repairman tried it himself. He was able to duplicate the
strange call immediately.
He went to the owner of the company and showed him what he'd found. The owner
said the guy at that extension was the company practical joker. He should send
him the bill for the $3,000.
Got a strange problem? Check the Call Accounting!
Very few technicians think of checking SMDR when there's a strange problem, but
sometimes it will lead you to the source of your problems very quickly.
Almost all modern phone systems have some type of SMDR or Call Accounting
built-in. If it's just SMDR, raw call data will come out a serial port that can
be fed into a PC with Hyperterminal (a serial communications program in
Windows), where you can choose the "save to disk" option to create a file of all
the calls in chronological order.
Got Windows Vista, 7 or 8 and no Hyperterminal? Take a look on google. You
can find information on the files you need to copy and what directories to put
them in from an XP PC. Sorry, I don't know what a MAC uses for serial
Don't have a serial port on your PC? We have a
to USB Converter that's worked on every computer we've tried it
on so far (these converters are not all created equal).