When it is time to replace the battery in your door/window sensor, you will see an alert on your system panel.
The DSC PG9945 door/window sensor requires a 3-volt lithium CR123A battery, which can be purchased at your local hardware, mass retailer, or battery store.
1. Locate the sensor with a low battery on either your system panel
2. Bypass the sensor on your panel
3. Insert a flat-edged screwdriver into the slot and push upward to remove the cover, then remove the screw and separate the cover from the base.
4. Remove and replace the 3-volt lithium CR123A battery.
5. Make sure the area where the batteries are stored is clean and there is no corrosion.
6. Put the cover back on starting with the opposite end from which it was opened, returning the screw then the outer cover. You should hear a snapping sound if it closes correctly.
7. Arm and disarm the system to clear the bypassed sensor.
8. Check if the low battery status has cleared