Essential Components and Transmission Modes in Communication Systems
Fundamentals of Data Communication Systems
Data Transmission Modes
These modes define the directionality of data flow between devices:
- Simplex Communication: If the roles of transmitter and receiver are clearly defined, data transmission is always carried out in one direction from sender to receiver. Example: Television (TV) broadcasting.
- Half-Duplex Communication: Communication may be bidirectional, but it cannot be simultaneous. Example: Two-way radio.
- Full-Duplex Communication: Two-way simultaneous communication. The transmitter and receiver act interchangeably. Example: Telephone.
Core Elements of a Communication System
- Issuer (Transmitter)
- The communication terminal element responsible for providing the information.
- Receiver
- An element of the communication terminal that receives information from an issuer.
- Terminal
- Terminals are connected through transmission lines, forming what is known as a data circuit.
Types of Communication Terminals
Classification by Intelligence
- Simple Terminals: A simple terminal has no intelligence whatsoever; it is totally controlled by an external process. Example: Monitor.
- Intelligent Terminals: They possess a certain capacity for independent processing. This type of terminal has its own processor and memory power to perform some previously established tasks. Example: Personal Computer (PC).
- Programmable Terminals: Tasks are assigned by loading a program from an external source.
Classification by Service Purpose
- General Purpose: They can develop a wide variety of functions. Example: PC.
- Specific Purpose: They meet only the specific function for which they were designed. This does not mean that their role is always fixed; thus, there are special-purpose terminals that are programmable. Example: Automated Teller Machine (ATM).
Auxiliary Devices and Signal Processing
- Transducer
- A device responsible for transforming the nature of the signal. Example: Light Emitting Diode (LED).
- Channel
- This component is responsible for the transport of the signal carrying the information exchanged between the transmitter and receiver. Defined from a telematics standpoint, it is characterized by its physical nature, the type of signal it can transmit, data rate, transmission capacity, noise level generated, length, etc.
- Modulators / Encoders
- Used to adapt signals to the transmission channels, especially when the signals and channels share the same nature.
- MODEM (Modulator / Demodulator)
- Responsible for converting digital electrical signals into analog electrical signals and vice versa.
- CODEC (Coder / Decoder)
- Responsible for properly coding digital electrical signals to fit the way required by the channel (always digital).
- Amplifiers
- In charge of restoring an analog signal back to its original amplitude, thereby mitigating losses caused by attenuation due to line length and, generally, all items affected by Ohm’s Law (R = V / I).
- Repeaters
- Whose mission is to regenerate digital signals. This is not an amplification but the reconstruction of a new digital signal.
- Distributors and Hubs
- In charge of distributing or mixing electrical signals between various senders and receivers.
- Switches
- Responsible for establishing an appropriate communication channel.
- Antennas
- Allow an electrical signal to spread through a wireless channel and, conversely, allow an electromagnetic signal to be collected in a cable.