DEFINITION MODULE TransferFunctions;

	(********************************************************)
	(*							*)
	(*	     Second order transfer functions		*)
	(*							*)
	(*  Programmer:		P. Moylan			*)
	(*  Last edited:	24 February 1991		*)
	(*  Status:		Mostly working, still testing	*)
	(*							*)
	(********************************************************)

TYPE TransferFunction;	(* is private *)

(************************************************************************)

PROCEDURE CreateTransferFunction (VAR (*OUT*) G: TransferFunction;
					SamplingInterval: REAL);

    (* Creates a new transfer function, with value initially set to unity. *)

PROCEDURE DestroyTransferFunction (VAR (*INOUT*) G: TransferFunction);

    (* Discards a transfer function. *)

PROCEDURE UpdateSamplingInterval (VAR (*INOUT*) G: TransferFunction;
					SamplingInterval: REAL);

    (* Recomputes the internal details of the transfer function to	*)
    (* allow for a change in sampling interval.				*)

PROCEDURE Filter (VAR (*INOUT*) G: TransferFunction;  input: REAL): REAL;

    (* Computes the output from G with the given input.  Remark: G is	*)
    (* an inout parameter because its internal state is affected.	*)

PROCEDURE EditTransferFunction (VAR (*INOUT*) G: TransferFunction;
						caption: ARRAY OF CHAR);

    (* Allows the keyboard user to alter a transfer function.	*)

END TransferFunctions.