How do I turn off the annoying chirp in the alarm system of 1998 XJ8?

To turn off the chirp in the alarm system of a 1998 Jaguar XJ8, you can typically do this by using the key fob. Lock the vehicle using the fob and then press and hold the unlock button for a few seconds until you hear a confirmation beep. If this does not work, consult the vehicle's owner manual for specific instructions or check the alarm system settings, as some systems may have a dedicated disable feature.