Calibrate Aftertouch

1. Access the Calibrate Sub-Menu (Edit -> X1 -> CAL -> Enter).
2. Select CCM and press Enter.
3. Press and hold key(s) with maximum force (Display shows 'Aft').
4. While holding, press the Snapshot button to set Threshold ('tHr').
5. Press Enter to store.

Source: Xboard 49 — emu-xboard-25-49-61-manual-eng (manual)