have a phillips cassette/radio player 4 my vectra. i need unlock cd changer?

hi, i have a phillips cassette/radio for my vectra.
my battery went dead so ive had to unlock my stereo which ive done successfully.
but i have no idea how to unlock the cd changer using the phillips radio.
any suggestions would bee very much helpful as weve been without a cd change for a year now, which is y its lead me to try this site :(
thankyou in advance