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


  ## 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 

  endif
  
  eqn="## No equation -- something wrong"; # Default

  if length(known)<2		# Invalid
    known = "  ";
  endif
  
  ## File containing data structure
  cbg_file = sprintf("%s_cbg",Name);

  if (exist(cbg_file)==0)
    error(sprintf("mtt_component_eqn: subystem \"%s\" does not exist", Name));
  endif
  
  ## Subsystem data structure
  cbg = eval(sprintf("%s;", cbg_file));

  if struct_contains (cbg, "ports")
    ## Combine ports with the other subsystems
    for [component_structure, component] = cbg.ports
      eval(sprintf("cbg.subsystems.%s=cbg.ports.%s;",component,component));
    endfor
  endif

    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);

      return
    endif
  endif
  

  ## Other causality representations
  if strcmp(causality,"effort")

	port_index = i;
	break;
      endif
    endfor

    ## File containing data structure
    NAME = mtt_subname(Name);
    Cbg_file = sprintf("%s_cbg",NAME);

    if (exist(Cbg_file)==0)
      error(sprintf("mtt_component_eqn: subsystem %s does not exist", NAME));
    endif
    
    ## System data structure
    Cbg = eval(sprintf("%s;", Cbg_file));
    
    
    ## And to which component (at higher level) is it connected?
    [new_Name,new_name] = mtt_subname(Name);
    port_bond = eval(sprintf("Cbg.subsystems.%s.connections(%i);", new_name, port_index));
    [in_name, in_port, in_bond] = mtt_other_end (new_name,port_bond,Cbg);

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

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


    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);

      ## Do the equations
      [eqn,insigs,innames] = eval(sprintf("%s_seqn (Name, name, cr, arg, outsig, insigs, innames);", comp_type));
    else			# Compound component
      new_NAME = Name;
      new_Name = mtt_fullname(Name,name);
      new_name = "";
      
      ## File containing data structure
      Cbg_file = sprintf("%s_cbg",new_Name);

      if (exist(Cbg_file)==0)
	error(sprintf("mtt_component_eqn: subsystem %s does not exist", new_Name));
      endif
      
      ## System data structure
      Cbg = eval(sprintf("%s;", Cbg_file));
      port_name = Cbg.portlist(port,:);

      LHS = varname(Name, outsig(1,1), outsig(1,2));
      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);
      
    endif
  endif

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

      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);

    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