Rocktron MIDI Xchange - Manual (Page 19)

Now preset number 1 is still selected. To select preset 35 depress
and release the RECALL switch. The display will now show the
number 35:
At this point - if you step on the RECALL switch again the MIDI
XChange will toggle back to the last preset - in this case preset
number 1. This function allows you to switch back and forth
between the last two presets selected - in this case preset 1: