function [known] = mtt_component_eqn (fullname, port, causality, ...
				      known, Cbg)

  ## function [known] = mtt_component_eqn (fullname, port, causality, known)
  ##
  ## Recursively finds the equations giving the signal of specified
  ## causality on the specified port of component named "name" within
  ## subsystem Name 

    if port>N_ports
      error(sprintf("port (%i) > N_ports (%i)", port, N_ports));
    else			# Get name and find equation
      name = deblank(cbg.portlist(port,:));
      if DEBUG
	disp("----> lower-level system")
      endif
      known = mtt_component_eqn (mtt_fullname(Name,name), 1, ...
				 causality, known, cbg);
      return
    endif
  endif
  

  ## Other causality representations

  
  ## A useful composite name
  name_port_cause = sprintf("%s_%i_%s",name, port, cause);
  full_name_port_cause = mtt_fullname(Name,name_port_cause);

  ## If value is known, don't do anything.
  if findstr(sprintf(" %s ", full_name_port_cause), known)>0
    eqn = sprintf("%s The %s signal on port %i of %s is known already", ...
		  CD, causality, port, name);
    return
  else			# Add to list
    known = sprintf("%s %s", known, full_name_port_cause);
  endif
  
  

  bonds = cbg.bonds;

  ## List of component bond causality (component-orientated causality)
  comp_bonds = bonds(bond_list,:).*directions; # Component bonds

  ## What components are at the other ends of the in bonds?
  ## Effort
  [in_e_bonds,in_e_components,in_e_ports,N_e] = mtt_component_inputs ...
      (name,comp_type,causality,"effort",comp_bonds,connections,cbg);
  ## Flow
  [in_f_bonds,in_f_components,in_f_ports,N_f] = mtt_component_inputs ...
      (name,comp_type,causality,"flow",comp_bonds,connections,cbg);


  ##Composite values
  N_ef = N_e + N_f;
  in_ef_bonds = [in_e_bonds; in_f_bonds];
  in_ef_components = [in_e_components; in_f_components];

    ## Find its equation
    if DEBUG
      disp("----> higher level system")
    endif
    

    known = mtt_component_eqn (mtt_fullname(new_Name,in_name), ...
			       in_port, causality, known, cbg);

    LHS = Source_seqn ("external",Name);
    RHS = varname(NAME, abs(in_bond), i_cause);
    eqn = sprintf("%s%s%s := %s;", LHS, SD, name, RHS);

    if !DEBUG
      comment = sprintf("%s PORT", CD);
      disp(sprintf("%s\n%s",comment, eqn));
    endif

  endif
  

  ## Handle special components
  if strcmp(comp_type,"0")||strcmp(comp_type,"1") # Junctions
    [eqn,insigs,innames] = junction_seqn (comp_type,Name, outsig, ...
					  insigs, innames);
  else				# Everything else
    if exist(sprintf("%s_cause", comp_type)) # Simple component
      ## Do the equations
      [eqn,insigs,innames] = eval(sprintf("%s_seqn (Name, name, cr, ...
						    arg, outsig, ...
						    insigs, ...
						    innames, is_port_output);", ...
					  comp_type));
      ## Resolve CR
      eqn = mtt_resolve_cr(eqn);

    else			# Compound component
      new_NAME = Name;
      new_Name = mtt_fullname(Name,name);

      RHS = Sensor_seqn ("external",new_Name);
      eqn = sprintf("%s := %s%s%s;", LHS, RHS, SD, port_name);

      if DEBUG
	disp("----> same-level subsystem")
      endif

      [known] = mtt_component_eqn ...
   	  (mtt_fullname(new_Name,new_name), port, causality, known, cbg);
      
    endif
  endif

  comment = ...
      sprintf("%s Equation for %s signal on port %i of %s (%s), subsystem %s.", ...
     	      CD, causality, port, name, comp_type, Name);

  if DEBUG
    disp(sprintf("%s\n%s",comment, eqn));
  endif
  
  is_external = mtt_is_external(comp_type,outsig, insigs, is_port_output);

      other_port = insigs(i,3);
      other_name = deblank(innames(i,:));
      if DEBUG
	disp("----> same-level component")
      endif
      

      [known] = mtt_component_eqn ...
    	  (mtt_fullname(Name,other_name), other_port, other_causality, ...
	   known, cbg);
    endfor
  endif

  ## Write this signal
  ##comment_2 = sprintf("Connected to:%s", in_component_list);
  if !DEBUG
    disp(sprintf("%s\n%s",comment, eqn));
  endif

endfunction