Tech 2 have two PCMCIA slots for memory cards. Only one of them can be used at time.
Current card can be switched using key combination on title screen:
Shift → Left or
Shift → Right.
This means press and release Shift, then press and release Left (or Right). Not the usual meaning of Shift-something, where you press Shift and hold it while pressing the other button. You may have to push and release Shift again after switching, as the light may stay on, affecting further inputs.