IBM 102 User Manual page 178

Unit Check Indicator
The Unit Check indicator has two operating conditions:
Off The printer has not detected any printer errors.
Blinking The printer has detected a printer error. The alarm beeps
(if not disabled). If the printer also displays a status code,
go to "Using the Status Code and Problem Listings" on
page B-2.
Operator Panel Keys
The operator panel has the following keys:
Menu/Adjustment Group
Darker/Enter
Lighter/Return
Menu
Micro /Scroll
Micro /Scroll
Quick Reference.
Operation Group
Cancel Print
Form Feed
Line Feed
Load/Eject
Set Top of Form
Start
Stop
Test
Models 102 and 1I1
– Display Address
– Hex Print
Model 4I3
– Display Interface
– Hex Print
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User's Guide