Free from memory, its been two years since I was on the MD80!
Its a garded good old fashioned flick switch.
In short ART can detect an engine failure and will then increase thrust on the operating engine.
To enable system sevaral requirements has to be met:
Aircaraft on ground and idle power
ART switch to auto
Slats extended
The ART system will arm when throttles are moved above about 60 to 65%N1 I forgot the exact number.
To disable flick switch off or retract slats.