Q. What do you mean by Companding?

Companding is the process of compressing and expanding. It comprises compressing the signal at the transmitter and expanding it at the receiver. The modulating signal to be transmitted is passed through an amplifier that has correctly adjusted non linear transfer characteristic, favouring small amplitude signals. These are artificially large when they are quantized and so the effect of quantizing noise upon them is reduced. Correct amplifier relations are restored at the receiver by expander. It's desirable to agree to some standard for companding in order to realize hardware efficiencies and to permit receiving and sending by a variety of users. The most common application of companding is in voice transmission. Japan and North America have adopted a standard compression curve called µ law companding. Law µ companding formula is given by

V_out= ( V_max X In (1+ µ V_in / V_max) / In (1+ µ)

 Where

 V_MAX= Maximum uncompressed modulating input amplitude.

 V_IN = Amplitude of the input signal at particular instant at time

µ = Parameter used to define the amount of compression

 V_out= Compressed output voltage.