Radio Shack TRS-80 Model 4 - Page 404

All output sent to *PR is still sent to *DU, even though *DU is
pointed NIL.
2. To remove the link between *PR and *DU, issue the command:
RESET *PR (ENTER)
The device table shows:
*PR =:> )< 'QlDE3'
*DU <=:> NIL
Now you have returned *PR to its original start-up condition, and
the link between
*PR and *DU no longer exists.
(You can type REMOVE *DU to remove *DU from the device
table.)
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