Casio TE-1500 Setup Manual page 21

NOTE:
Upon the Subtotal key depression the cash register will go out the
COM port designated above and look for the credit card device. The cash
register will display "INITIALIZING PAX".
If the cash register connects with the credit card device then "PAX
Initialized" message will appear.
If the cash register fails to connect with the credit card device the message
"PAX Init Fail!" message will appear.
1) Turn the mode lock key on the cash register to the PGM position
2) Enter "4" from the numeric keyboard and hit the Subtotal key
Tender Key Programming
TE-2200 Keyboard
21