Message Quality and Quantity:
Quality of transmission is a very important .consideration in telecommunication. Voice communication can use a narrow bandwidth, which means the reproduction of sound is not of high fidelity because the human ear is adaptable and can discern words even if not entirely faithfully reproduced. The same is not true for the transmission of music, where we expect high quality sound; for television broadcasting, where our picture must be sharp and the quality of colour high; and especially for data transmission, where inaccurate bit transmission can result in garbled and worthless messages.
There are many techniques, besides providing more bandwidth than actually needed, to improve transmission quality and reduce the noise. One such technique is multiplexing. Multiplexing is of two types: Frequency Division Multiplexing, (FDM) and Time Division Multiplexing (TDM). Frequency Division Multiplexing is used to split a channel into several discrete narrower ones for simultaneous but separated transmission. On the other hand, time division multiplexing uses a common channel for several messages but at intermittent times; each signal taking turns on the same channel. In other words, multiplexing is a technique that is often used to interleave data so that they can be carried more efficiently in the same bandwidth. It is similar to concentrating but replaces many lines with one transmission path of .greater capacity. It must be remembered that multiplexing is a sharing technique only. There is no increase in the total information than can be transmitted.