Quantizing Distortion in PCM Systems Caused by Digital Attenuation

The use of digital switching centers in combination with analog transmission networks may lead to situations where additional losses must be introduced at some points to maintain the selected transmission scheme. By using purely digital methods, such as recording of PCM code words, to produce the losses, analog-to-digital conversion may be avoided. In the present paper, the quantizing distortion caused by digital attenuation is calculated for losses of 1, 3, 5, and 6 dB, using the 13-segment encoding law. Two recording methods are discussed, showing that the SNR values of the methods may differ by as much as 2.3 dB for specific losses.