On the SAR Flight at Coltishall it was not uncommon to have a police observer (with a police radio) in the back of the Wessex when we did some of the overland searches for missing people. I think there was talk of a mod to put a dedicated fitting in for the radio or aerial but don't know the outcome of that. There was certainly no training of observers at the time, although two or three of them were ex-aircrew.