This audio compander circuit schematic is equiped with NE575 produced by Signetics, it is working with a 3 – 7V battery and has a current consumption of 3.5mA at 3V and 5mA at 7V. The companding process ( input compression, output as expander) is improving the signal/noise ratio on a communication line.
NE575 contains 2 ic’s , pins 1 to 9 works as expander and the 11 to 19 pins can work as expander or compressor or automatic load control ( ALC ).
NE575 has a a high input sensitivity, the maximum input level is 1.5Vef. This compander covers a frequency domain from 20Hz to 20KHz, the total distorsions are below 1% and the signal/noise ratio is 80dB.