An association has 15 voting members. Executive meetings of this association can be held only if more than half (i.e., at least eight) of the members are present (i.e., eight is the minimum quorum required to hold meetings). Classified matters can be discussed and voted on only if two-thirds of the embers are present. The chairman can cast two votes if the quorum is met and an even number of members (including the chairman) are present. Above the room door there are three lights— GREEN, BLUE, and RED—to indicate the quorum status. Derive an SM chart for a system that will indicate whether a minimum quorum has been met (GREEN), classified matters can be discussed (BLUE), or a quorum has been met and an even number of members are present (RED). GREEN and RED lights may be lit at the same time or GREEN, BLUE, and RED lights may be lit simultaneously. Assume that there is a single door to the meeting room and that it is fitted with two photocells. One photocell (PHOTO1) is on the inner side of the door, and the other (PHOTO2) is on the outer side. Light beams shine on each photocell, producing a false output from the cell; a true output from a photocell arises when the light beam is interrupted. Assume that once a person starts through a door, the process is completed before another one can enter or leave (i.e., only one person enters or leaves at a time). If PHOTO1 is followed by PHOTO2, a sequencer generates a LEAVE signal and if PHOTO2 is followed by PHOTO1, the sequencer generates an ENTER signal. At most one ENTER or LEAVE will be true at any time. Assume that these signals will be true until you read them. Basically, you read the signal and provide a signal to the door controller indicating that the door is READY to let the next person in or out. 

(a) Draw a block diagram for the data section of this circuit. Assume that ENTER and LEAVE signals are available for you (i.e., you do not need to generate them for this part of the question). 

(b) Draw an SM chart for the controller. Write the steps required to accomplish the design. Define all control signals used.
(c) Draw an SM chart for a circuit that generates ENTER and LEAVE.