An apparatus is disclosed. The apparatus comprises a primary power supply (PPS) configured to supply primary power, a PPS sensor configured to measure the power supplied by the PPS and provide a PPS measurement signal indicating an amount of the power supplied by the PPS, a backup power supply (BPS) configured to be provided in an emergency data system and further configured to supply backup power to a modem, and an integrated circuit configured to maintain a clock using the power supplied by the PPS. The integrated circuit is configured to receive the PPS measurement signal from the PPS sensor, determine whether the PPS measurement signal falls below a threshold, and maintain the clock using the power supplied by the BPS in response to a determination that the PPS measurement signal has fallen below the threshold.