RS Flip Flop

  Circuit Operation:  Transistors Q1 and Q2 switch

  between Saturation and Cutoff.  S1 and S2 are two

  Single-pole Single Throw switches (SPST).  Turning on

  S1 cuts off Q1 and Q2 gets into saturation so that LED

  D1 turns on.  On the other hand if S1 is off and S2 is

  turned on Q2 will be in cutoff and Q1 gets into saturation

  turning LED D2.  D1 ON  means that the output at the

  collector of Q2 is low and the opposite output at Q1 is high.

  D2 ON means exactly the opposite situation.