I've had an alarm system installed for about a month now.
Twice, it has failed to give me any audible sign that it has
armed when I use the Lock button on my key fob.

Normal operation is such that, when I press Lock twice,
it locks the truck, signals one normal horn beep which
indicates it has locked, followed by a shorter half-beep
which indicates that the security system has armed.

But, as I said, twice it has failed to emit the half-beep.
When this has happened, I have not been in a situation
where it is convenient to test to see whether it is actually
armed (such as by opening the door without the fob).

I am just wondering if anyone else has had this problem.