In the event of a power failure, entire buildings or parts of them may be rendered useless. Not only obvious, direct power consumers such as IT or lighting depend on the power supply; all the infrastructural equipment used today depends directly or indirectly on electrical power. That includes lifts, air conditioning systems, alarm systems, security gates, automatic door locking units, sprinkler systems, and private branch exchanges for telephones. Even the water supply on floors above or below ground is dependent on electricity due to the necessary pumps.