an integrated circuit , in which some areas of the chip are powered from battery , but at least two other areas of the chip can draw power from independent on - chip power - storage capacitors . the signal line &# 39 ; s input buffer draws power from one capacitor , and the decoder logic draws power from another . thus , even if the first capacitor is depleted by the signal line &# 39 ; s staying in the high - current regime , it will be powered up again when the signal line is again driven high ; and the charge stored in the second capacitor will permit the decoding logic to operate . preferably the second capacitor also powers circuitry which encodes a unique serial number for the chip . thus , even after the battery has died , the chip can be interrogated to ascertain its unique serial number .