Using the Arm Delay Mode
Why does my system chime for a minute or two before it arms?
The system will chime for 60 seconds after pressing the "Arm Away" button to allow you time to leave the house before the system arms. If you would rather arm it instantly, move the "Max/Min" switch on your handheld remote to "Min" and press "Arm Away." This will arm the system immediately, with one chime (Instant Mode.)
Alternately, you can arm the system in one chime using the keychain remote, which always arms it in Instant Mode. Arming from the "Arm" button on the main console will always arm the console in Delay Mode.