If your phone rings and seems to work but one party cannot be heard by the other, the problem is often the result of a defective handset cord. You can test this very quickly by removing the handse cord and switching it with a cord that you know works. If that solves the problem, replace the cord with a new one.

If this problem is occurring with an electronic phone handset, check your owner's manual--there may be an audio volumn control or a mute button causing the problem.