POTS Operation Precautions

POTS performance is greatly affected by the quality of the line being used. Precautions must be taken to ensure the Tieline codec is not sharing the line with other devices. Please remove these possible sources of interference:

 

•DSL or ADSL Modems

•Other telephone handsets

•Portable phone base stations

•Unused parallel phone sockets

•Fax machines

•Computer modems

•Burglar alarm systems

•Extension bells

•Call waiting

 

Call Waiting

Call waiting tones may cause the codec to malfunction. Most phone companies supply call waiting as a feature and you will need to turn it off. Your Telco should be able to provide a number you can dial to disabling the call waiting feature on the line.

 

Private Branch Exchanges

Avoid connecting the codec to a digital PBX or PABX system, key station, business system or any other local switchboard. It may sometimes be tricky to detect if you are connected to one of these systems, however, as a general guide, these devices require you to dial an additional digit to access the POTS network.  

 

 

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.

4.Tieline recommends that you confirm your broadcast POTS line works well before you try to go live.