Beeinflussungsmechanismen bei Zeitmultiplex-Übertragungs- und Vermittlungssystemen durch hochfrequente Signale

The process by which high-frequency interference (primarily from AM and FM broadcasting facilities, but also from HF portions of rapid digital signals used in transmission and control) arriving at the scanner of PAM or PCM time-division-multiplex telephone systems can reach the baseband as alias spectra with the same amplitude is modeled mathematically. The description is based on the scanning theorem itself, with no limiting assumptions; numerical solutions are presented for both AM and FM interference signals. Further analysis, including human noise-response factors, reveals that 90 dB of damping between the four-wire/two-wire division point and the PCM scanner are required to assure qualitatively good transmission. It is suggested that such damping can be achieved by combining properly constructed repeating coils and active matching circuits with SC or digital filters.