Does the DSC PG9901 use batteries or an AC power source?
The PG9901 operates on battery power. The device uses long-life lithium batteries. The batteries are 3.6V 14.5AH lithiums and they will last, on average, 8 years before you replace them. The siren itself has low battery detection and will send a low battery signal back to the main panel so you will never have to guess at when you should replace them.