Buzzing, static and interference:
VoIP static, interference and buzzing is usually associated with the introduction of a signal or voltage into the VoIP connection that is then converted into an annoying sound. In many cases the problem exists within the devices that are connected to the ATA (i.e. DUO). In some cases a hum or noise may be coming from an IP phone. Cordless phones can be susceptible to interference from other wireless devices transmitting on the same frequency. If you are experiencing this type of issue the first thing to do would be to disconnect everything from the phone port of the ATA. Then connect one simple corded phone directly to the ATA. If the buzz or static sound is gone then look at one of these possibilities:
Cordless phones can generate static if the signal is weak. Weak signals between the base station and handset can be caused by too great of a distance between the two or weak batteries in the handset. Another possibility could be interference generated by another wireless device.
A device that could be introducing electrical voltage such as a caller ID device, or another device.
Using an incorrect power supply that has a different voltage.
Using an improper DC power adapter or one that has ground problems.
Having distributed the VoIP though out the premise without disconnecting the incoming line at the demarc.
An alarm system not integrating correctly with the VoIP.
A dial-up modem device that is trying to dial out through the VoIP line.
A baby monitor. These devices can broadcast on a similar channel to your phone.
Check the power supply and not only make sure that it appears correct (has the manufacturer's name on it), but is the correct voltage and amperage. Linksys equipment has different power supplies for different routers. Check to make sure that if you have two pieces of equipment from the same manufacturer that you are using the correct one. You may need to check the manuals. For an RT31P2 you should be using a 12VDC and 1000ma power supply. When using one that came with perhaps a wireless router (sometimes 500ma) you will experience static on your phone. Prolonged use of an incorrect power supply could damage the ATA and/or router.
When getting new equipment it would be a good idea to tape a piece of paper with the device's name on the power supply itself (for instance Linksys router). We also suggest that you tape a tag at the end of the DC power cord, as this will make it easy to recognize the correct power supply when reconnecting equipment.
Connecting the VoIP service into the premise's wiring, which has not been physically disconnected at the demarc, could result in the VoIP equipment receiving voltage, which would very well damage the ATA. If you have not already disconnected the previous telecom's wiring at the demarc, and want to connect into the wall jacks, then you will need to do so. If you have already disconnected at the demarc, there should be no voltage being introduced into the premises telephone circuit, other than that which the VoIP is creating. For information about testing for problems with your phone lines do a GR-909 test.
Some devices that can introduce voltage and actually interfere with your VoIP service are:
Separate caller IDs
Faults with the wiring throughout the premise can also cause noise or buzzing throughout the lines. Some conditions can create the following:
Buzzing: Interference can be caused by one or more wires that may have come into contact with metal, (other than the connection terminals).
Static: Wires that could be loose at a connecting point. Check all wires and connections for secure connections.
Dead Air: Can be the result of wires crossed or coming in contact with another pair. (For example a red wire crossed with a green wire if 2-pair wire is being used.)
If the buzzing still occurs after a corded test phone was connected directly to the IAD, then look at these possibilities:
Do you have the correct power supply that came with the device?
Try plugging in the power supply into another 110volt source.
If all these possibilities have been checked and the issue is still occurring, then the noise may be actually coming from the ATA itself.