Audio Systems: Sony XR-6859 Alarm / Cassette Problem, sony xr, volkswagen golf

Question
Due to a cassette being jammed in my Sony XR-6859 (original fitment to my 1998 Volkswagen Golf), immediately after fitting a new car battery. I have undone the retaining screws on the head unit, however, an alarm has now triggered which I cannot reset. Do I somehow need to input the serial code from the head to stop it. I assume this alarm is a standard fitment, it is not linked to my car alarm, and doesn't stop when the battery is disconnected ?

Once resolved how do I remove the stereo without setting the alarm off again to remove the cassette ?

Thanks

Answer
Sorry, I was out of town.

You will likely have to input a security code which would be a dealer only thing (they will need the serial# off the head unit).
*If you still have all of the paperwork from the dealer, the code should be in that.

It should require this code anytime the batttery is dissconnected.

J Mael