This document discusses three types of communication methods: 1) Simplex which allows transmission in one direction using a one-way channel, 2) Half Duplex which permits transmission in two directions but only one direction at a time using a two-way channel, and 3) Full Duplex which enables simultaneous two-way transmission using a four-wire line.

1. 3
1. One-Way Simplex
) simplex
Simplex
2. Either-Way of Two
Ways Half Duplex) Half Duplex
Walkly-
Talkly
Haft Duplex Two-Wire Line)
Half Duplex
3. Full-Duplex)

2. Four-
Wire Line
Full-Duplex