Computer Science for IGCSE & O level - Data Transmission (Section 1 - No. 34)
What is a disadvantage of echo checks?
It is not a good method for detecting errors.
It takes more time to send and receive the data.
It requires the same key for encryption and decryption.
It can only detect single-bit errors.
Объяснение
Echo checks take more time to send and receive the data because of the time used to echo the data back to the sender.