The GTN750 – now quite common and a very capable and powerful GPS/Com/Nav and quite a lot more! Here displaying a flight track from Guernsey to Fowlmere via ORTAC.
‘Touching’ the STBY frequency allows a new frequency to be entered using either on screen keypad (appears automatically) or by turning the Frequency Selector knob (Bottom Right) – thereafter Touching the ‘Top’ Frequency ‘flip flops’ the STBY Frequency into use.
Dick Rochfort (Garmin) has a useful YouTube tutorial area.
I can offer familiarisation training on the GTN650/750 and GNS430/530 series.