What is the cause of static on the line?

Static or buzzing noises on your line can only occur on the analog side of the phone system. This analog segment consists of your phone and phone cable. Once the signal is sent through the phone adapter, it is digitized and can no longer create static or buzzing.

Try replacing the telephone cable and/or telephone. Cordless telephones can generate static due to a weak signal-connection between the base of the telephone and the handset. Weak signals can be due to low batteries in your handset, or the recommended range between the handset and base station has been exceeded. If you are using a wireless router, try moving it away from the Phone Adapter as each wireless device may interfere with each other.