What does ac mean on my adt security keypad?

On your ADT security keypad, "AC" typically stands for "Alternating Current," which indicates that the system is receiving power from an electrical source. If the "AC" indicator is lit or displayed, it means the system is functioning normally with adequate power supply. If the indicator is off, it could suggest a power issue or that the system is running on backup battery. Always check your user manual for specific meanings related to your model.