1. CSE, IT– III SEM Course Name-DAC Topic- Communication modes

2. 2 Digital and Analog Communication Section C Standards in data communication

3. Syllabus Section C: Standards in data communications: 1.Communication modes: simplex, half duplex, full duplex; 2.Transmission modes: serial-, parallel-transmission; synchronizations: Asynchronous-, synchronous- transmission; 3.Type of services: connection oriented-, connectionless- services; 4. Flow control: unrestricted simplex protocol, simplex stop- and -wait protocol, sliding window protocol; 5.Switching systems: circuit switching; picketing switching: data gram, virtual circuits, permanent virtual circuits. 6.Telephone Systems: PSTN, ISDN, asynchronous digital subscriber line. 7.Multiplexing: frequency division-, time-, wave- division multiplexing

4. COMMUNICATION MODES

5. Modem DATA TRANSMISSION Media DTE 1 DTE 2

6. COMMUNICATION MODES It defines the direction of signal flow between two linked devices (transmitter and receiver).

7. A data transmission mode is the manner in which data is sent over the underlying medium DATA TRANSMISSION MODE

8. COMMUNICATION MODES SimplexHalf DuplexFull Duplex Full / Full Duplex COMMUNICATION MODES SimplexHalf DuplexFull Duplex Full / Full Duplex COMMUNICATION MODES SimplexHalf DuplexFull Duplex Full / Full Duplex COMMUNICATION MODES SimplexHalf Duplex Full / Full Duplex COMMUNICATION MODES A communications mode is classified as under (depending on the direction of transfer of data )

9. 9 A simplex mechanism can only transfer data in a single direction. Only one of the two devices on a link can transmit; other can only receive. Examples a) broadcast radio or television b) Keyboard can only input c) Monitor can only accept output. The simplex mode uses the entire capacity of the channel to send data in one direction Simplex Mode Communication

10. Simplex, Half-Duplex, and Full-Duplex Transmission 10

11. Full-Duplex M ODE C OMMUNICATION allows transmission in two directions simultaneously It is analogous to a voice telephone conversation in which a participant can speak even if they are able to hear background music at the other end. In full duplex mode. Signals going in one direction share the capacity with signal going in other direction. The sharing can occur in two ways: Either the link must contain two physically separate paths, one for sending and other for receiving or The capacity of the channel is divided between signals travelling in both directions.

12. 12 Half-Duplex A half-duplex mechanism involves a shared transmission medium The shared medium can be used for communication in both direction but the communication cannot proceed simultaneously. An additional mechanism is needed at each end of a half- duplex communication that coordinates transmission to ensure that only one side transmits at a given time Entire capacity of a channel is taken by whichever of the two devices is transmitting at the time. Walkie-talkies and CB radio - only one side can transmit at a time and are half duplex system.

13. allows communication in two directions at the same time but not between the same two stations. Full/Full-Duplex M ODE C OMMUNICATION Tx/ Rx Satl No direct link One station sends to a second station and third station receives. Used in multipoint communication systems

14. Simplex, Half-Duplex, and Full-Duplex Transmission 14