I spotted this. However, Chris [the actor] is very obviously careful throughout the rest of the episode to stay away from solid objects: we never see another character using this apparatus, so it could be hologrammatic.
Me and my friend talked about this slip-up and my friend and I agreed that the radio was hologramatic. There are a lot of slip-ups throughout the series and you just have to assume that the ship was designed for holograms.(why not. Seeing as they have holograms on the ship!)
Throughout the series, you can clearly see Rimmer's hologram appearance change many times, (including a change of hair style) He also is seen with holographic books appearing in his hands that only he can read. It is quite possible that Holly allowed a holographic radio to appear in Rimmers grasp which allowed him to directly interface with the real radio.
The button is not hologramatic, but it is light sensative, thus allowing bot hologram's and real people to use the buttons in starbug and around the ship.
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