Depends too whether the beacon has a modulated carrier ie a tone superimposed onto the RF carrier signal or, as above, a beat frequency oscillator, BFO, is required to enable the pilot to hear a tone where no tone is on the carrier.
As I understand it...
One has the audio tone ident on the transmitted signal, the other the carrier is just a carrier keyed (no audio) with the ident and the tone is added at the receiver by beating 2 frequencies together making it audible.