Time-division multiplexing (
TDM) is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fraction of time in an alternating pattern. This form of signal
multiplexing was developed in
telecommunications for
telegraphy systems in the late 19th century, but found its most common application in
digital telephony in the second half of the 20th century.