Do not answer calls I don't know. Looked this up, here and google but no info. Sad there are those out there that call, never leaves messages, and continue to call even though they never get a live person! Back in the day, (60's, 70's), telephones were used for keeping in touch with friends and family. Now, our homes are invaded by unknowns calling all day and some well into the late evening! Disgusting!