Index: mttroot/mtt/lib/comp/simple/SS_cause.m
==================================================================
--- mttroot/mtt/lib/comp/simple/SS_cause.m
+++ mttroot/mtt/lib/comp/simple/SS_cause.m
@@ -16,14 +16,22 @@
 % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % %% Version control history
 % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % %% $Id$
 % %% $Log$
+% %% Revision 1.1  1996/11/01 12:18:38  peterg
+% %% Initial revision
+% %%
 % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 
 % Copyright (c) P.J. Gawthrop, 1996.
+
+% Check that there is exactly one bonds.
+if check_bonds(bonds,1,'SS')==0
+  return
+end
 
 if (bonds(1)==0)|(bonds(2)==0) % Under causal
   status = -1;
 else                          % causal
   status = 0;

Index: mttroot/mtt/lib/comp/simple/TF_cause.m
==================================================================
--- mttroot/mtt/lib/comp/simple/TF_cause.m
+++ mttroot/mtt/lib/comp/simple/TF_cause.m
@@ -16,12 +16,21 @@
 % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % %% Version control history
 % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % %% $Id$
 % %% $Log$
+% %% Revision 1.1  1996/11/01 12:05:54  peterg
+% %% Initial revision
+% %%
 % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 
 % Copyright (c) P.J. Gawthrop, 1996.
+
+% Check that there are exactly two bonds.
+if check_bonds(bonds,2,'TF')==0
+  return
+end
+
 
 %Causality of TF is same as that of a junction
 [bonds,status] = zero_cause(bonds);