Standby or emergency lighting system - timer set by duration of power failure controls high and low charging levels

摘要

A security lighting system and power supply operates when the normal supply fails. The power supply is obtained from rechargeable batteries provided with a charging circuit capable of supplying a high current as may be required after a normal supply failure, and a low current intended to maintain the battery charge. The systeme employs discrete autonomous blocks each housing such a charging, lighting and switching ability. A central control system activated by a fall or recovery in the normal supply voltage has its own auxiliary supply etc. and includes a timing device which measures the duration of the failure and then operates in reverse providing a high charge rate until the timer returns to zero.