Exit illuminating system

Claim 1

An exit illuminating system for leading persons to an escape route under emergency conditions, comprising: means for connecting the system to an alternating current power line; a rectifier circuit for converting said alternating current power into direct current; a battery; means connecting said direct current from the rectifier circuit to the battery so as to provide a substantially continuously available charging current to said battery when alternating current is present on said power line, said means including a current control transistor in series between said converted direct current and said battery for controlling the charging current supplied to said battery, and a biasing circuit including said battery connected to said current control transistor in order to bias the degree of conduction thereof in accordance with the battery voltage; a smoke sensor for developing an electrical activating signal when the surrounding atmosphere in an area to be protected contains a predetermined amount of smoke; a high intensity light source coupled to said electrical current source and adapted for mounting adjacent an exit, said light source being responsive to the activating electrical signal by the smoke sensor for providing a high intensity illumination sufficiently visible through the smoke in such atmosphere so as to guide persons who may be trapped therein to an escape route via the exit; and means connecting said battery to said high intensity light source whereby direct current is made available to said light source during both the presence and failure of alternating current on the power line, thereby to render such system fail-safe in the event of power line failure.