ERA-DCKIT-2 
This applies to the following ERA transmitters (ERA-DSTX, ERA-UTX, ERA-PIR)
-The ERA-DCRX (receiver) has four-zone indicator lights that blink when triggered.
-When the battery is low in a transmitter paired to a corresponding zone, the zone indicator LED for that light will blink for 10 minutes when that zone is triggered.
-When the battery is low in a transmitter paired to a corresponding zone, the melody for that zone will play twice (normally the melody will play only one time).
For the ERA-PIR-SPK: when the battery is low, the melody will play twice, instead of once.