It could be that your phone and jacks are not the problem, but rather, other home electronics could be interfering with your service.
Equipment that can interfere includes satellite TV receivers, computer modems, caller ID boxes, fax machines, and alarm/security systems.
Typical symptoms of interference include noise on the line, cross talk/other conversations, busy tone while talking, and intermittent dial tone.
To test your equipment:
- Unplug your phones from both their jacks and electrical outlets.
- Unplug any other equipment that uses a jack.
- After you've unplugged all your equipment, wait one minute and then plug a corded phone into each jack — testing one jack at a time.
You should hear a clear, strong dial tone when you test each jack. If you don't, make a note of which piece of equipment is plugged in and what you heard when you tested the jack.
If you're finding interference but don't want to unplug the offending piece of equipment, try installing a radio suppresser or radio/noise filter on your line.