Alarm/immobiliser fun.....

[ElectricDogs]

I have two Defenders, a 1998 2.8i and a 2010 Puma. I bought the Puma 5 years ago, it's a slightly pimped commercial which came with an aftermarket central locking system and manual immobiliser but no alarm fob; I sort of assumed being a commercial it wasn't fitted with an alarm and haven't given it much thought since. The 2.8i came with 2 fobs, the battery in one of which packed up yesterday. Not having a new battery handy I grabbed the spare, which I hadn't used up to now. Imagine my surprise when both Defenders responded! This raises a few questions - 1. I had assumed that any given fob/10AS combo would operate on a discrete channel and whilst not unique to a vehicle, how come one of the fobs operates both vehicles and the other only the 2.8i? 2. I would obviously prefer to have discrete fobs for each vehicle. I can buy fobs on eBay and elsewhere, but how do I go about making sure each only operates one vehicle? 3. Flush with my newly discovered functionality on the Puma, will the 10AS need to be reprogrammed to operate the door lock actuators (the rear is a genuine LR one, the other two aftermarket, but they are simple 12v devices and work fine on the same system)? It would make sense to use one fob if possible.

I appreciate these are slightly dumb questions but I never really gave this any thought before...so help/advice would be greatly appreciated.