Abstract :
It is shown that for waveforms of simple shapes certain features may be defined: content, epoch, spread, skewness, squatness, etc., which are affected in a very simple way by passage through a linear system (which is regular* at low frequencies). In fact, by proper definition, they are affected only additively by constants which are independent of the applied waveform, and characteristic only of the system. These invariants for the pulses and for the system, correspond to the cumulants used to describe statistical distributions. With due care, these results can be usefully generalized for a.c. wave-packets.
