An APL control EPROM appears to be present on the Temperature Compensation board, but the computed checksum failed to agree with the memory. This may occur at power-up or during any system initialization.
What you should do:
To clear the error, click Clear error in the XYZ Display window.
To clear it using an RCU-II, press and hold down the Servo Power Off button and then press the Joy button twice.
If the error reoccurs, contact your Giddings & Lewis service representative.