Logic circuits are classified in two broad categories. What described thus far have been grouped as combinational logic circuits. The other category is the sequential logic circuits which are extremely valuable because of their memory characteristics. The basic building block of the sequential logic circuit is the flip-flop (F/F). Flip-flops are also called bistable multivibrators or latches.

There are several types of flip-flops : the RS F/F, the D F/F, the JK F/F and the T F/F. Among these flip-flops there are also clocked F/F and master-slave F/F. Only the simplest RS flip-flop built from NAND gates will be covered in this introductory course. The suggested applications are taken from Section 2 of the I.S.M.E.C. Electronics 13-16 Projects Manual [Ref.5]. Students must try to connect and test all the circuits in this part during their practical sessions.