Section 8: POTS Operation and Usage Tips
T
ieline
Page
66
T E C H N O L O G Y
As an example, a POTS service has been provided to a customer a long way
from the CO, this customer has since moved on. The phone company needs
to provide a phone service in the same area, but closer to the CO. Let us
assume half way. The service is provided, however the phone company
simply jumpers the new service onto the old (further) service. The cable from
the jumpering point to the old service point is redundant and will act as a
stub, loading the line down. This will not matter for a phone service.
However it will affect the performance of a
T
ieline
codec connected to the
line.
A common variation of this problem is in high rise buildings. Most high rise
buildings have a MDF
10
in the basement and a series of smaller IDFs
11
on the
floors. If a line was originally used on an upper floor, it would have a
connection from the CO to the MDF and then from the MDF to IDF for the
appropriate floor. Over time the service could be redeployed to a lower floor.
However, for a quick installation the phone company may not disconnect the
upper floor IDF, they could just bridge into the lower floor IDF leaving the
upper floor IDF still connected. The unused stub from the lower to upper
floors could then cause problems.
8.7.
Earth Leakage Problems on the Line
A good line should have an earth isolation of better than ten meg-ohms. If your
line is located in an area where water is a problem, ask your Telco to check out
the earth leakage.
8.8.
Equipment Problems at the CO or Local Exchange
Although there are many factors at the Telco end that can cause problems, a
problem that does occasionally occur is that the clock on the interface codec to
your line is not synchronized to the network. A drifting clock will cause instability
and unreliable codec performance. If you suspect that this could be the problem,
contact your local Telco
.
The
T
ieline
family of codecs is designed to achieve solid and reliable operation
with a line quality of 30% or better. On most good POTS lines,
T
ieline
G
3
codecs
will normally achieve 28,800 bps and a line quality of approximately 50% or
greater. If you are not able to achieve this level of operation, you may have
transmission problems with your line or the line at the other end of the
connection. Using the
T
ieline
test facility on 317 913 6911 (USA) will assist you
to find where the problem lies.
10
MDF Main Distribution Frame.
11
IDF Intermediate Distribution Frame
