Instron 4400 Series Operator's Manual page 121

(b) Press the G.L. RESET key to reset the EXTENSION
display to zero.
(c) Drive the crosshead up with the JOG key until the re-
quired spacing is displayed (in inches or millime-
ters), and again press the G.L. RESET key to enter
the new gauge length into system memory.
If the AT G.L. LED had been flashing, indicating that a
power shutdown or system reset had occurred, it be-
comes steady when the G.L. RESET key is pressed. This
LED goes out whenever the crosshead is moved from
gauge length, but relights when the crosshead is returned.
Note
Once gauge length has been set, the
crosshead will always return to this position
upon a RETURN command.
Establish Gauge Length
5-29