comms 1 lec

• Human communication is the process of exchanging information, with main barriers being language and distance.
• Communication systems consist of basic components such as a transmitter, channel or medium, and a receiver, with noise degrading or interfering with transmitted information.
• A general model of all communication systems includes a transmitter, communication channel, and a receiver.
• The transmitter in a communication system is a collection of electronic components and circuits that converts the electrical signal into a signal suitable for transmission over a given medium.
• Transmitters are made up of oscillators, amplifiers, tuned circuits and filters, modulators, frequency mixers, frequency synthesizers, and other circuits.
• Applications of channel 2 include Simplex, AM and FM broadcasting, digital radio, TV broadcasting, digital television (DTV), cable television, facsimile, wireless remote control, paging services, navigation and direction-finding services, telemetry, radio astronomy, surveillance, music services, internet radio and video, and the Internet of Things (IoT).
• Duplex applications of channel 2 include telephones, two-way radio, radar, sonar, amateur radio, citizens radio, family radio service, the Internet, wide-area networks (WANs), metropolitan-area networks (MANs), and local area networks (LANs).
• The low-frequency limit of channel 2 is 54 MHz, what is the upper-frequency limit?
• The communication channel in a communication system is the medium by which the electronic signal is sent from one place to another.
• Types of media include electrical conductors, optical media, free space, and system-specific media (e.g., water is the medium for sonar).
• A receiver in a communication system is a collection of electronic components and circuits that accepts the transmitted message from the channel and converts it back into a form understandable by humans.
• Receivers contain amplifiers, oscillators, mixers, tuned circuits and filters, and a demodulator or detector that recovers the original intelligence signal from the modulated carrier.
• A transceiver in a communication system is an electronic unit that incorporates circuits that both send and receive signals.
• Examples of transceivers are telephones, fax machines, handheld CB radios, cell phones, and computer modems.
• Signal attenuation, or degradation, exists in all media of wireless transmission and is proportional to the square of the distance between the transmitter and receiver.
• Noise in a communication system is random, undesirable electronic energy that enters the system via the communicating medium and interferes with the transmitted message.
• Electronic communications are classified according to whether they are broadcast, narrowband, or broadband.
• The telephone is an example of this type of communication.
• Analog or digital signals are types of electronic communication.
• Examples of analog signals are sine wave, voice, and video (TV) signal.
• Most electronic communication is two-way and is referred to as duplex.
• The form of two-way communication in which only one party transmits at a time is known as half duplex.
• Many transmissions are of signals that originate in digital form but must be converted to analog form to match the transmission medium.
• Baseband information can be sent directly and unmodified over the medium or can be used to modulate a carrier for transmission over the medium.
• Examples of half duplex communication are police, military, etc. radio transmissions, Citizen band (CB) radio, Family radio, and Amateur radio.
• Modulation and multiplexing are electronic techniques for transmitting information efficiently from one place to another.
• Most digital signals use binary or two-state codes.
• When people can talk and listen simultaneously, it is called full duplex.
• An analog signal is a smoothly and continuously varying voltage or current.
• In telephone or intercom systems, the voice is placed on the wires and transmitted.
• One-way (simplex) or two-way (full duplex or half duplex) transmissions are types of electronic communication.
• Digital signals change in steps or in discrete increments.
• Multiplexing allows more than one signal to be transmitted concurrently over a single medium.
• The electromagnetic spectrum is divided into segments: 1-5: The Electromagnetic Spectrum
• A radio-frequency (RF) wave or radio wave is an electromagnetic signal that is able to travel long distances through space.
• 300-3000 MHz Ultra High Frequencies (UHF) are used for TV channels 14-67, cellular phones, and military communication.
• The simplest method of electronic communication is referred to as simplex.
• The optical spectrum exists directly above the millimeter wave region.
• Modulation makes the information signal more compatible with the medium.
• 30-300 GHz Extremely High Frequencies (EHF) are used for satellite communication, computer data, and radar.