Insert sim card ( after converting sim into 2G , use only BSNL, Airtel , VI sim , Does not support JIO sim) and make call to sim number and start listing audio 
Inbuilt battery - 300mAH battery inbuilt for backup time 15 to 90 minutes depends on 2G signal strength in that area 
Built in door magnet , can be connected to door window alarm  siren if door window alarm make sound device will make call to predefined mobile number 
Small time up to 30 minutes automatic recording using 32GB class 10 memory card