The old fob looks like this. Notice the pins on the rear. This is the bit that you push in to turn the alarm off if the batteries in the fob die. Dunno why its been replaced as there very good alarms. Mine is anyway. Has anti hijack, panic, auto door closure the lot. Works a mile off and is loud as fcuk!
(http://img292.imageshack.us/img292/4687/alarmfob4lh.jpg)
(http://img14.imageshack.us/img14/5367/alarmfobback9jp.jpg)