IBM 102 User Manual page 202

When a test is not running, pressing Return or Cancel Print tells the
printer to exit test mode and perform a partial reset. If you press
Return, the printer goes to online not ready; if you press Cancel
Print, the printer goes to online ready.
Pressing Enter or Start begins a test. Some of the tests print and
then exit back to the Operator Print Tests menu automatically, while
other tests require you to give input using the operator panel keys to
complete the test. See the individual test descriptions on the
following pages for specific instructions.
While a test is running, pressing Stop or Cancel Print halts the test.
If you press Stop, the display returns to the Operator Print Tests
menu. If you press Cancel Print, the printer exits test mode,
performs a partial reset, and becomes online ready.
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User's Guide