I haven't tried your way, but I really like the equation editor method. I was able to generate a ringing effect using the equation below.

By the way, what language does this equation editor use, are there any references out there on how to setup variables, functions, etc .. ?

{ Use this template to create your own signals } Function Signal(t); Begin A:=0.0005; m:=1; fm:=200000; fc:=5500000; k := 0.0000005; mysig1:= 2/2.71828183^(t/k); Signal := mysig1*A*((1+m*cos(2*pi*fm*t))*cos(2*pi*fc*t));