In communication, Multiplexing is a set of techniques that transmit signals from several sources over a single communication channel in order to minimize the cost of communication channel. Various techniques of sharing a communication channel among a large number of users have been devised. These are known as multiplexing techniques. Signals are basically multiplexed using two basic techniques frequency division multiplexing and time division multiplexing
Frequency Division Multiplexing (FDM)
In FDM the frequency range is divided to form logical channels with each user having exclusive possession of the assigned channel with a separate frequency value.