We have a number of phones in the house....none works. When the phone is picked up all you get is a buzzing sound

This could be any number of things here are a few ideas to help isolate the problem:

1. Disconnect all phones from the wall jacks
2. Connect a phone to each wall jack, one at a time and test. This will help you determine if one of the all jacks is bad. Use the same phone for testing each jack. If you have a phone that does not require AC power, use that phone to test. If the same phone works at every wall jack, one of your phones is bad. You can now test each phone alone until you find the bad phone.
3. If after testing each wall jack, you still have buzzing on the line you will need to contact the telephone company to test the line coming into the house or apartment.
4. If you live in a house and can access the "box" where the phone lines enter the house, there is usually a jack where you can plug the test phone into and check the lines BEFORE they enter your home.
5. If you test at the entry box and your phone works, you have a problem with the wires in your home. If you still have the buzzing, it is probably a telephone company problem