Crosstalk in time-division-multiplex communication systems using pulse-position and pulse-length modulation

The crosstalk caused by a multi-stage resistance-capacitance-coupled amplifier is determined for time-division-multiplex communication systems using pulse-position modulation (p.p.m.) and pulse-length modulation (p.l.m.). The results are compared with those obtained for pulse-amplitude modulation (p.a.m.). The bandwidth of the amplifier is assumed to be so large that the crosstalk caused by distortion at low frequencies and that caused by distortion at high frequencies can be determined independently. The crosstalk caused by low-frequency distortion is less when p.l.m. is used than when p.a.m. is used and the crosstalk for p.p.m. is less than that for p.l.m. The crosstalk caused by high-frequency distortion is usually negligible except between channels whose pulses are adjacent. The crosstalk for p.p.m. is worse than that for p.a.m., especially if the time constant of the amplifier is either very small or very large. The crosstalk for p.l.m. using front-edge modulation, is worse than that for p.a.m. when the time-constant of the amplifier is small, but better when the time-constant is large.