The ancient Greeks established lines of signal towers at mountain-tops. At each one, a large fire was to transmit a signal to the next tower, and in this way, information was passed on through the land. Al almost anything that makes a noise has been used for signaling. A kind of drum talk is still used in Ce Africa today, although few who are not natives have been able to understand it. The sender uses a dru that can produce a high or low tone. Because the local dialect alternates in these tones, the sender is a simulate speech with the drums