No "low battery' warning
Recently I noticed one of my door sensors showed to be constantly "open', but I had not received a "low battery' warning. Opening the door resulted in the double blink from the sensor, but no audible beep was noted, and the indication still showed as "open'. Replacing the CR2032 battery resolved the problem. Why did I not receive a "low battery' warning? Is the sensor defective? Everything seems to be operating OK now, but I am left with a lack of confidence in my system. Does the daily test signal sent to the mother ship check for things like these?