Few days ago I took a flight to go back to my town. Towards the end of the journey, the captain demanded us to shut down any electronic device that we had on board, including iPods, CD players, phones and so on. Reason: there was very low visibility and we had to start the instrumented landing.

From what I could understand, an instrumented landing system allows and aircraft to be centred on the lane assisted by signals delivered by an ILS (a localiser and a glide slope), so to arrange the maneuver without visibility. This signals are in the 110 MHz (LOC) and 330 MHz (GS) frequency range.

Given that for the take off, "manual" landing and the journey itself, shutting off the devices is not required any longer (and there are signals travelling even there I would guess, at least for what concern communication with the base and all the ariplane intra-components communications), why is that instead required for an assisted landing? What interferences could a CD Player possibly produce on the instrumentation to an extent that it's more dangerous than with the usual take off - flying - landing phases?

On a side note: as you probably understood, my level of expertise is very low, so forgive any dumb mistake or oversight.