Land Rover Repair: Land Rover alarm question, discovrey, passcode number

Question
We have a 1996 Land Rover Discovrey 4x4 with 110K miles. It was not driven for months and the battery died. We installed a new battery, but now, we can't turn the alarm  off. The remote key device does not work.  We have a passcode number, however we don't how to use it to dismantle the alarm. Any suggestions?

Answer
If this is a US market truck, you ae going to have to haul it to a dealer or a specialist with a T4 or Autologic system.  One of those systems is needed to talk to the alarm control unit.  And until that's done, the alarm prevents the truck from starting.