So, 12 pulses are transmitted, and if they are base 10, that's 10^12 possible combinations. I suspect that 5 may be the biggest 'digit' available though, and it's possible that the first and last digit (and possibly more) are pre-amble and maybe a check bit, which narrows down the possible combinations to 5^10....which is still quite a lot!
The code number is stored in the alarm ECU somewhere (obviously mine will be different) but I've no idea where, or how to read it.
But a possible way of determining the code would be to build something that transmitted similar pulses in some kind of ascending order.
Given that the pulse lasts about 0.03 seconds, rattling through them in order would take over 81 hours to try all permutations
So...some further rationalising of the problem is required. Not to mention building the transmitter device.
Having some more fobs would be handy, to see if there are any patterns in the code. For example, if only 8 of the numbers changed, the problem could be solved in just over 3 hours
Dunno if I'll take this any further. If I do, I'll keep it updated
And before anyone says it, yes I know I can send my alarm ecu away with £100 and it'll come back two shiny new fobs