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408 Genie Distribution WNET Manual v3
© Tieline Research Pty. Ltd. 2020
the PBX is not digital, the performance of the codec is unlikely to be as good as a normal
POTS line.
If you have no option other than to use a PBX or PABX System, search for a fax machine. The
overwhelming majority of fax machines are designed for analog POTS line operation and are
normally on an extension optimized for fax machines and data transmission. Substitute a
normal phone for the fax machine to verify correct operation. Use a normal phone, not a venue-
supplied phone, because this may have characteristics to match the existing PBX/PABX and
not a POTS line. After confirming correct phone operation, you can unplug the phone and
attach the phone line to the codec.
Check the Length of the Line
It is desirable to have a local loop which is as short as possible, i.e. the line from your location
to the local Central Office or Local Exchange. Optimum performance can be expected for lines
up to about 2 miles (3 kilometers) in length. Line quality will be reduced over longer distances
and the codec can be expected to perform at lower bit rates. Line quality will also be affected by
the age, condition and type of cabling used, e.g. plastic insulation or paper insulation, water or
moisture entering the cable, age and state of repair of joins.
POTS Party Lines or Stubs
In some countries, it was the practice to have more than one phone service attached to one line
- sometimes called a 'Party Line'. As more lines are installed, services are separated but the
redundant cabling may remain connected across the line, causing problems with the operation
of your codec.
Leakage Problems on the Line
A good line should have an earth isolation of better than ten mega-ohms. If your line is located
in an area where water is a problem, ask your Telco to check out the earth leakage.
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.
POTS Exchange Problems
On most good POTS lines, Tieline codecs can achieve a 28.8kbps connection at a line quality
of approximately 50% or greater. If you are not able to achieve this level of operation, you may
have a problem with your line, or the line at the other end of the connection.
Tips for Successful POTS Operation
1. Take a phone when you are doing a remote broadcast. Connect it to the line you want to use
and dial the number to check for any unusual noises. If present, these may be caused by other
devices connected to the line.
2. Take an ADSL/DSL filter to all remote locations. ADSL/DSL modems can generate noise on a
line which will degrade the performance of your codec. Simply place the ADSL/DSL filter
between the POTS line and your codec to remove the interference.
3. Tieline USA has a POTS test codec you can dial on +1-317-913 6911 to facilitate line tests at
each end of your connection to diagnose line problems.