Six original Cambridge-style questions on error detection after transmission, with worked solutions.
Explain why data should be checked for errors after it has been transmitted.
The 7-bit values 1100101 and 1110000 are to be sent using even parity, with the parity bit as the leftmost bit. Write the two bytes that are sent.
A system uses odd parity. These bytes are received: 10110110, 01001111, 01101001. Identify which byte contains an error and explain how you know. State one type of error a parity check would not detect.
This parity block was sent using even parity. One bit was changed during transmission.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | |
|---|---|---|---|---|---|---|---|---|
| Byte 1 | 1 | 0 | 1 | 1 | 0 | 1 | 1 | 1 |
| Byte 2 | 0 | 1 | 1 | 0 | 1 | 0 | 0 | 1 |
| Byte 3 | 1 | 1 | 0 | 1 | 0 | 0 | 1 | 1 |
| Parity byte | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 |
Identify the bit in error and write the corrected byte.
Describe how a checksum is used to detect errors in transmitted data.
Describe how an echo check works, and give one disadvantage of it.
Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.