PURPOSE: To provide an uninterruptible power supply which receives a busy signal from each automatic tellers machine when a customer is operating the automatic teller's machine or an automatic cash dispenser and which stops upon finish of operation of last customer.

CONSTITUTION: Among the signals (a), (b), (c) fed, respectively, from the contact A of an automatic tellers machine or an automatic cash dispenser, the contact B of a commercial power supply detecting circuit 2 and the contact C of a battery voltage drop detecting circuit 3, the signal (a) is fed through a NOT circuit 5 to an AND circuit 4 whereas the signals (b), (c) are fed directly to the AND circuit 4 and NOT circuits 6, 7. Output of the AND circuit 4 is fed directly to the self-holding relay 11 of an uninterruptible power supply 10 which is connected through a one-shot circuit 9 with the output of the AND circuit 8.