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1. The output of a logic gate is 1 when all its inputs are at logic 0. The gate is either

(A) A NAND or an EX-OR

(B) An OR or an EX-NOR

(C) An AND or an EX-OR

(D) A NOR or an EX-NOR    (Ans)

Hints and Solution :  The output of a logic gate is 1 when all inputs are at logic 0. The gate is either a NOR or an EX- NOR.

Truth Table for NOR Gate

Truth Table for EX-NOR Gate

2. What is the simplification of the following Boolean expression in a Product-Of-Sum form?

(A) Out = (A+B+ NOT(C)) (A+NOT(C)+ D) (C+NOT(D))

(B) Out = (A+B) (A+NOT(D)) (B+NOT(C)+D)

(C) Out = (B+C+ NOT(D)) (A+C+ NOT(D)) ( NOT(C)+D)        (Ans)

(D) Out = (A+NOT(B)+D) (C+D) (B+NOT(C)+D)

Hints and Solution : Transfer the seven maxterms to the map below as 0s.

Map the 0s as they appear left to right top to bottom on the map above. Now form groups of cells.

The final result is product of the three sums i.e.

Out = (B+C+ NOT(D)) (A+C+ NOT(D)) ( NOT(C)+D)

3. What is the appropriate form for the given k-map?

(A) F(W,X,Y,Z) = Σm (0,3,4,6,8,10,11,12,14)

(B) F(W,X,Y,Z) = Σm (0,2,5,6,8,10,13,14,15)       (Ans)

(C) F(W,X,Y,Z) = Σm (1,2,5,6,8,9,11,14,15)

(D) F(W,X,Y,Z) = Σm (1,2,3,7,9,10,11,14,15)

F(W,X,Y,Z) = Σm (0,2,5,6,8,10,13,14,15)

4. How many fibres are required by a unidirectional and bidirectional ring respectively,to support their working traffic?

(A) 1 and 1

(B) 2 and 1

(C) 2 and 2

(D) 1 and 2       (Ans)

Hints and Solution :  SONET rings can be classified by the routing principle and the SONET overhead used for triggering protection switching. A ring is called a unidirectional ring if bidirectional working signals follow opposite physical routes around a ring , while bidirectional working signals in a bidirectional ring follow the same route. Due to this routing principle, a unidirectional and a bidirectional ring, require one and two fibers respectively, to support their working traffic.

5. Find odd one out related to transmission media cables?

(A) Basic rate ISDN can transmit data at a rate of 512 kilobits per second on an existing local telephone line.      (Ans)

(B) A T1 line is a dedicated telephone connection of 24 channels.

(C) A T1 channel can be configured to carry either voice or data traffic.

(D) Cable modems provide high-speed transmission over cable TV lines and are shared by many users.

Hints and Solution :  Each ISDN line is made up of separate 64-Kbps "channels" for sending and receiving calls, plus a channel that is used primarily for sign