>
> Hey guys,
> I just noticed that the db levels on one of our PM3s is lower than the
> other. I hate to ask for a phone lesson, but I could stand some
> enlightenment on this. Below are reading from the PM3s. The first one is
> located at our place the other is located at a remote pop. They had a bad
> storm last night and we lost the Point to Point T1 and the PRI both on the
> one with the low db levels. Should I be screaming at the phone company or
> does the PM3 possibly have a problem?
Probably neither.
These numbers appear to reflect the line build-out values for the CSU
portion of the Livingstons.
When the T-1 is terminated by the phone company, the voltage level at the
demarcation point is set to a reference value. Your equipment can apply a
"line build out" factor to compensate for cable losses. If the received
signal is, say, 7.5 dB below the reference (-7.5) at your receiver, then
it is logical to assume that if the signal left the phone company's
equipment at 0, there is 7.5 dB of loss in the line (cable) between their
handoff and your equipment.
In the old days, one would take a sophisticated level meter, measure the
received level, and set switches on the equipment to compensate.
Alternatively you could measure the length and type of cable between the
telco jack and the CSU, and look up the build-out value on a chart.
More modern gear has the level measuring hardware built in, and sets the
line build-out (compensation for cable losses between you and telco)
automagically. So, the differences may be that the telco's demarc box is
close to the PM-3 at your facility, and further away at the remote end, or
the telco installer set the output to -10 or so.
The receive level of between -7.5 and -15 isn't anything to be concerned
about, well within spec assuming that you're using good quality twisted
pair cable to interconnect the unit to the telco's jack (Use cat. 5, NOT
flat silver cords!)
-- Jay Hennigan jay@west.net --
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