Response::usage = "Response[ transf, Input, s, {TimeVar, StartTime, EndTime}, gopts]: Plots the output of transfer function `transf' with Laplace input signal `Input'. The Laplace variable is `s'. The output graph uses the variable `TimeVar' and starts at `StartTime' and ends at `EndTime'. Returns the output variable as a function of time `t'.";
SecOrder::usage = "SecOrder[zeta, wn, t]: Gives the unit step response value at time instant t for a standard second order system wn2/(s2 + 2z wn s + wn2) with the damping ratio z=zeta and natural frequency wn =wn. Returns instantaneous value of the step response output variable at time instant `t'.";