Vehicle mounted terminals usually have an external reader attached - which can be a hand held reader bolted to part of a forklift, or a proper fixed mounted industrial scanner - or both.

Fixed mounted readers can read barcodes on shelf edges and gives the driver the go ahead signal to lift that pallet.

Attaching a long range hand held scanner is the most flexible option. But make sure you give your drivers good safety advice - you don't want people hanging out of forklift windows, trying to reach barcodes.