ISRO2007-22

Question

Phase transition for each bit are used in

• A. Amplitude modulation
• B. Carrier modulation
• C. Manchester encoding
• D. NRZ encoding

Answer 1

Answer is C

In the Manchester encoding, a logic 0 is indicated by a 0 to 1 transition at the centre of the bit and a logic 1 is indicated by a 1 to 0 transition at the centre of the bit.

Original Data                   Value Sent

Logic 0                   0 to 1 (upward transition at bit centre)

Logic 1                   1 to 0 (downward transition at bit centre)

For example, The pattern of bits " 0 1 1 1 1 0 0 1 ", the Manchester code will be 01 10 10 10 10 01 01 10

Comments

Thank you for the explanation in simple and understandable form. Can you please explain about other options i the question also? Thanks in advance

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If anyone is confused with this answer, know that there are two versions of Manchester encoding, the one in the answer is Manchester by G. E. Thomas, and the other one is Manchester as per IEEE 802.3, which is the opposite of the one in the answer, i.e. Logic 0 means a 1 to 0 transition and logic 1 means a 0 to 1 transition.

Answer 2

ans is (c)

The Manchester code is therefore sometimes known as a Biphase Code. A Manchester encoded signal contains frequent level transitions which allow the receiver to extract the clock signal using a Digital Phase Locked Loop (DPLL) and correctly decode the value and timing of each bit.