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Time-division multiplexing

Time-division multiplexing

(also TDM)

Time-division multiplexing definition

Multiplexing is a method networks use to consolidate multiple digital and analog signals into one. These signals are transported over a medium (like a fiber optic cable or radio wave).

Time-division multiplexing (TDM) is one of the several multiplexing techniques and is most commonly used in digital telephony. TDM involves putting multiple data streams in one signal by separating it into many segments, each with a very short duration.

Types of time-division multiplexing

  • Synchronous TDM. With synchronous time-division multiplexing, the multiplexer assigns every device an equal time slot at all times, whether or not the device has any data to send. The device has to transmit the data during the assigned time slot. If it doesn’t have any data to send, its time slot remains null. Another device can’t use this time slot.
  • Asynchronous TDM. Also known as statistical division multiplexing, asynchronous TDM is a multiplexing method in which the allocated time slots are not permanent (unlike in synchronous TDM). Time slots for transmitting data are assigned only to the machines that have information to send.

TDM application examples

  • Television broadcast
  • TDM telephone network
  • The GSM telephone system

Further reading

Ultimate digital security