The core principle behind CRC is remarkably consistent, whether used in computer networks or telecommunications. The process involves a pre-agreed mathematical formula (called a “generator polynomial”) that both the sender and receiver use.

Here is the fundamental, step-by-step process:

1. Sender’s Role: The sender takes a block of data, known as a “message block,” and performs a calculation on it using the generator polynomial. This calculation produces a short sequence of check bits, which is the CRC value or “fingerprint.”
2. Transmission: The sender transmits the original data block, incorporating these newly calculated CRC check bits into their designated positions within the frame structure.
3. Receiver’s Role: The receiver accepts the incoming transmission, separating the data block from the sender’s CRC check bits. It then performs the exact same calculation on the data block it just received.
4. Verification: The receiver compares the CRC value it just calculated with the CRC value it received from the sender.
   • If the two CRC values match, the data is considered error-free, and the transmission is successful.
   • If the two CRC values do not match, the receiver knows that a transmission error has occurred.

While this principle is universal, the G.704 standard applies it in slightly different ways depending on the transmission speed and specific frame structure being used.