Last weekend in the middle of the night, the Dexcom G4 transmitter failed. Either it doesn't send out an audible signal, it was on vibrate (I didn't think to check it at the time but I usually have it on hypo repeat at night), or I slept through it. It was first used mid-January, so by using this forum, I learned that it was at the end of it's usable life and ordered a new one, which has arrived. In the mean time, I restarted the old one and it is in operation right now. I have some questions and was wondering if anyone could have time to share and teach me these things: 1. Does the receiver give an audible alarm when the transmitter itself fails? In other words, did I just somehow miss it or does it just quit and only give a visual error? 2. Under "Device Info", it says the battery is OK. Would you continue to use the old one or go ahead and switch to the new? We have decent insurance, and should not have difficulty getting two a year, but it does cost $140 per replacement. I want to make sure to "use up" the old transmitter but without the danger of it just quitting with no alarm. I am considering just going ahead and switching it tomorrow when the sensor is at one week because my son wants a sleepover at a friend's house and I want it to be reliable. Still, I would like to ask this for future reference. 3. Would you see any bad readings with a failing transmitter before it altogether failed? I know sensors can start giving ??? and off readings, but not sure about transmitter. Thank you.