The operation of a traditional left-to-right transducer can be simulated by a head transducer by starting at the leftmost input symbol and setting the positions of the first transition taken to a = 0 and fl = 0, and the positions for subsequent transitions to o~ = 1 and fl = 1.
we can illustrate the fact that head transducers are more expressive than left-to-right transducers by the case of a finite-state head transducer that reverses a string of arbitrary length.