The document discusses various methods for error detection in digital communication, including: 1. Parity checking, which adds an extra parity bit to ensure an even or odd number of 1s. Two-dimensional parity divides data into a grid and adds a redundant row. 2. Checksums, which divide data into sections, add the sections using one's complement arithmetic, complement the sum, and send it along with the data for verification. 3. Vertical redundancy checking adds a parity bit to each character to detect single-bit errors and some multiple-bit errors. It is often used with ASCII encoding.

7. (1) Parity Checking: