The term Companding is a combination of Compressing and Expanding, meaning it does both. This is a non-linear PCM approach that compresses the information at the transmitter and extends the same data at the receiver. By using this approach, the effects of noise and crosstalk are minimized.
Companding techniques occur in two ways. They are:
A-law Companding Technique
• At A = 1, where the characteristic curve is linear and no compression is performed, uniform quantization is achieved.
• A-law has the original mid-rise. It also includes a value that is non-zero.
• For PCM telephone systems, A-law Companding is used.
µ-law Companding Technique
• At μ = 0, where the characteristic curve is linear and no compression is performed, uniform quantization is achieved.
• μ-law has the mid-tread at the origin. Hence, it has a value of zero.
• Companding by μ-law is used for speech and music signals.