Akai QX-D2400 Operator's Manual page 20

Safeguard Against Accidental Erasure
When a new recording is made, any program material previously recorded is automatically
erased and only the new recording remains. To safeguard valuable recordings from being
erased accidentally, the cassette and the deck are equipped with a special device.
On the back of the cassette there is an erase prevention tab on each side. To prevent
accidental erasing, break out these tabs with a screwdriver. If only one side of the tape
is to be protected, break out the tab on the left side with the side desired facing you.
To record on a tape in which the tab has been broken, place a piece of cellophane tape
over that area.
NOTE:
When a tab is broken out, the RECORD key cannot be depressed.
GB 19