Originally Posted by Steve_C
Your phone lines run off of a voltage. Its about 50volts DC. This voltage is what powers your telephone as long as its one that doesn't plug into the wall. You may have a bad line in your home that is causing electrical noise which will interrupt the voltage and cause similar problems. The best thing to do is to first contact the telephone company and have them do a test on your line up to your home. They should do that for free. If they test and all is well then its some wiring from the junction box to the inside of the house. Before testing make sure nothing is plugged in to the phone line. Fax and modems will sometimes autoanswer or inhibit testing.
Here is a bit of info about telephone wiring. There is usually about 2 to 4 solid wires that will run from an outside junction box to the jack inside the home. they are twisted a bit which helps prevent interference from the adjacent lines and other noise sources the wire may sit next to.
Now when your telephone company sends a caller to to you via their switchboard a ringing voltage is placed on the wire. If your touch it you will get a shock as its an AC voltage that causes a plunger to strike back and forth a bell inside most older phones and the newer phones just detect the voltage and cause a speaker to wail instead. Now I suspect that you have dirty contacts somewhere in your house or perhaps at the junction box. A broken line will also cause a problem. If you have a broken line you will have intermittent contact until the current reaches maximum then the wire will disconnect. This happens a lot with wiring in homes as mice and other things will damage wires. The phone company repair man has testing devices that will check for these things and if you ask nicely sometimes they will check it for you. If all else fails you need to contact the phone company and pay the professional to come out and diagnose the problem.
I have installed telephone and internet and used use those fancy devices.
Good luck.
Steve C.