Debugging is controlled by the data cards DEBU and DBUG. DEBU is the standard GEANT data card which defines the event numbers to be debugged (see p. ...). Once the event range for debug is set by DEBU, the detector specific debugging can be activated by the DBUG card. For the tracker we can have for example DBUG 'TRAK' 3. The numerical parameter defines the level of printing. The value can be accessed in the code through CALL DCVALU('DBUG','TRAK',IV).