Final answer:
Even parity is a form of error detection where a parity bit is added to make the total count of 1s even. In a successful transmission, the receiver counts an even number of 1s. In unsuccessful cases, an error is either detected due to an odd number of 1s or goes undetected if additional errors mimic even parity.
Step-by-step explanation:
When even parity is used in data communication, an additional bit is added to the end of a binary message to make the total number of 1s even. The receiving end checks this to determine if the data has been received correctly or if there has been an error during transmission.
Example a) Successful Transmission:
Original data: 1011001 (4 ones, even)
Parity bit added: 0
Sent data: 10110010
The receiver counts the number of 1s. There are 4, which is even, so the data is considered correctly received.
Example b) Unsuccessful Transmission with Error Detection:
Original data: 1100101 (4 ones, even)
Parity bit added: 0
Sent data: 11001010
Error during transmission: data received: 11011010 (even parity check fails)
The receiver counts 5 ones which is odd, hence an error is detected.
Example c) Unsuccessful Transmission without Error Detection:
Original data: 1010101 (3 ones, odd)
Parity bit added: 1 to make it even (now 4 ones)
Sent data: 10101011
Error during transmission: One bit is flipped: received data: 11101011
The receiver counts 5 ones which is odd but assumes an even parity and incorrectly adds a bit to make 6, missing the error, thus failing to detect it.