I am in the process of changing head decks

The one I am taking out (pioneer) has a small diode on the accessory switched power wire - I am replacing it with a shop ex-demo Alpine (CDA-9883) but it doesn't have this, just a wire straight into the plug

Do I need it? Since the Alpine doesn't have it I didn't think so but though it may have been cut off in error by the store? - also it doesn't have a fuse on this switched line (only the main constant feed) should it have one here?

On the constant feed there is also some type of coil? between the fuse and the head deck in a platic plastic case?

Cheers for any advice

The diode is most likely a protection thing to stop 'keep alive' power from the deck finding its way back to the switched supply when the ignition is off. It can't hurt to include one - something like the 1N4001 will be fine - but if there's no power on the lead from the head unit when the rest of the unit is plugged up but the ignition is off, then there's no need for it. I'd be *very* surprised in this day and age if it were necessary.

The coil is simply and inductor to stop high frequency noise from the ignition and injector circuits, the alternator, and the wiper motors finding their way into the supply for the radio.

Neil