Hi does anyone know how to unlock a Sony cassette stereo (old style XR C450RDS model or similar) because the one in my sister's car has locked recently since the battery was changed! Basically it is stuck in Date mode and nothing else will work! She doesn't have the manual and I can't find it on the web so are there any clever people out there who know the normal procedure for unlocking Sony units i.e what buttons to press? There is a sticker on the back of the face but I wasn't sure how to use this! Thanks in advance!