module spring1d(n1,n2);
 inout n1,n2;
 kinematic n1,n2;
 parameter real k = 10 from (0:inf);    // spring constant given in n/m
 parameter real l = 0.1 from (0:inf);   // length of spring in m

 analog
   F(n1,n2) <+ k*(Pos(n1,n2) - l);

endmodule