1suppose that the following 9bit messages were received in a

1.suppose that the following 9-bit messages were received in a parity check code. which messages are altered during transmission?

a) 101010101 b)101101101 c) 000000000

Solution

If an odd number of bits (including the parity bit) are transmitted incorrectly, the parity bit will be incorrect. This indicates that there was a parity error in transmission. Assuming that the last bit is the parity bit, let us examine all the messages:

a) The count of 1 bits is 4 so the parity bit has to be 0. The last bit here is 1 so the message is   incorrect, i.e. there is an error;

                b) The count of 1 bits is 5 so the parity bit has to be 1. The message is error free.

               c) The count of 1 bit is 0 and the 0 bit is 8, so the parity bit has to be 0. The message is error free.

2. Odd Parity:

a) The count of 1 bits is 4 so the parity bit has to be 1. The message is error free.

b) The count of 1 bits is 5 so the parity bit has to be 0. There is an error in transmission.

c) The count of 1 bit is 0 and the 0 bit is 8, so the parity bit has to be 1. There is an error in transmission.