The SN74LS279AN is a 4 basic S\-R\ Flip-flop Latch. Under conventional operation, the S\-R\ inputs are normally held high. When the S\ input is pulsed low, the Q output will be set high. When R\ is pulsed low, the Q output will be reset low. Normally, the S\-R\ inputs should not be taken low simultaneously. The Q output will be unpredictable in this condition.