deactivated and decade counter output 34 2 34 pin 4 is activated full power start up of the lamps is finished and the step wise reduction of power begins with decade counter output 34 2 34 pin 4 advanced to a high state by decade counter ic3 current flows to the base of transistor q9 turning it on the activation of transistor q9 allows current to flow through the led portion of optically isolated triac driver oc9 from transistor q1 the lighting of the led portion of optically isolated triac driver oc9 activates the phototriac internal to oc9 and switches resistor r38 into bridge circuit br2 the added resistance of resistor r38 in bridge circuit br2 increases the time required for timing capacitor c12 to charge to the breakover voltage of diac 1 consequently scr3 and scr4 are fired after the beginning of the incoming ac signal half cycle resulting in less than full power being applied to the lamps however the resistance value of resistor r38 is such that the charging time of timing capacitor c12 is not greatly affected and therefore a large portion of the ac signal is conducted to the lamps when decade counter output 34 2 34 pin 4 is deactivated and decade counter output 34 3 34 pin 7 is activated transistor q9 turns off and current flows to the base of transistor q8 turning it on the activation of transistor q8 allows current to flow through the led portion of optically isolated triac driver oc8 from transistor q1 the lighting of the led portion of optically isolated triac driver oc8 activates the phototriac internal to oc8 and switches both resistors r38 and r37.