Emergency traffic light control

Claim 1

An emergency traffic light control apparatus for auxiliary operation of traffic lights upon failure of a primary AC power source comprising: an auxiliary DC power source, an inverter connected to said DC power source for converting said DC power to AC power to operate said traffic lights when said primary AC power fails, said inverter including solid state circuitry comprising a square wave inverter trigger including a relaxation oscillator and flip-flop, a pulse transformer for stepping up the pulse emitted from said inverter trigger connected across the output of said inverter trigger, an inverter output transformer, a parallel square wave SCR inverter circuit including two SCRs the anodes of which are connected to the primary of said output transformer, two diodes of which the cathodes are connected to said primary of said output transformer, means to connect the anodes of said diodes and the cathodes of said SCRs to the negative terminal of said DC source, means to connect the positive terminal of said DC source to a center tap in the primary of said output transformer, the output from said pulse transformer adapted to drive the gates of said SCRs, said SCRs when firing producing a square wave AC voltage across the secondary of said output transformer, and an inductance capacity network connected across said secondary to produce a sinusoidal wave at 60 cycles from the 60-cycle square wave originating at said transformer''s secondary terminals, a relay means energized by said AC power source, said relay means including a first switch means arranged such that when deenergized said first switch means connects said DC power source to said inverter and a second switch means arranged such that when energized said second switch means connects said AC power source to said traffic lights and when deenergized said second switch means connects the output of said inverter to said traffic lights.