Electronic Communication Chapter 6

What is Electronic Communication? Transmission of information using electricity Electromagnetic Wave: a wave created by electric and magnetic fields; it travels through the air like ripples in a pool of water. Telecommunication: communication over a long distance

Transmission Channels Transmission channels are the paths over which messages must travel to get from the sender to the receiver Copper wire Coaxial cable Optical fibers Electromagnetic waves

Copper wire

Coaxial cable

Optical fiber

Electromagnetic Waves Amplitude: the height of a wave measured from the top of its peak to the bottom of its trough. It is an indicator of the strength of the wave Frequency: the number of waves that pass through a given point in one second. It is commonly measured in a unit called a hertz (Hz). One hertz is equal to one complete wave cycle in one second.

Electromagnetic waves Electromagnetic Spectrum

Sending and Receiving Signals Transmitter: A device that encodes (changes) signals into sine waves for broadcast on radio waves or micro waves. Receiver: A unit that collects waves and decodes the information contained within those waves. Modulation: The superimposition of sine waves on electromagnetic carrier waves. Satellite: A device that orbits the earth and receives messages from one location and transmits them to another.

Modulation

How the Telephone Works Sound waves cause vibrations that can be encoded into signals Older phones: Older phones: Sound waves from voice caused flexible piece of metal (diaphragm) to vibrate, diaphragm pressed against carbon granule and produces a varying electrical current. Receiver contains wire-wrapped iron core, connected to it is a flexible metal diaphragm. When transmitted electrical signal enters receiver it travels through the coil and magnetizes the iron core forming an electromagnet. The magnetic field pulls on the metal diaphragm, it vibrates and produces the sound Transmitter in mouthpiece Receiver in earpiece

Electronic Telephones Digital electronic devices Integrated Circuits Redial Redial Speed dial Speed dial Caller ID Caller ID Voic Voic Call forwarding Call forwarding Portability Portability Affordability Affordability

Cellular Telephones Radio waves Operating area (cell) Transmission tower Transceiver Transmitter and receiver combined into a single unit Transmitter and receiver combined into a single unit

How Radio Works Mass communication Antenna transmits signal Radio waves assigned a certain frequency Radio antenna picks up waves that have that frequency Circuitry separates carrier wave from sound signal (demodulation) Speaker changes boosted electrical signal into sound

Satellite Radio Digital Audio Radio Service (DARS) Digital signals are transmitted in satellites and radio receivers on the ground Signals broadcast over large area and captured by receivers in many locations Digital technology makes it possible to encode additional information Receiver can display artist information such as name of song and artist Subscription 100+ channels 100+ channels Commercial free Commercial free

How the Television Works Electronic system of transmitting pictures and sounds over a wire or through the air.

The Television Camera The television camera is also known as a camcorder. The camera converts images and light (video) and sounds (audio) into electrical signals that can be recorded to magnetic tape, discs, or memory cards Allows playback

Audio and video recorded separately Microphone – sound Charge – Coupled Device – images and light Charge-Coupled Device (CCD): A very small solid state panel that contains light sensitive photosites or photodiodes. The CCD uses the photosites to convert light into electrical signals that are then transformed into an image.

Light reflected from image enters camera lens Lens focuses light on CCD Amount and color of light hitting each photosite on CCD determines the electrical charge produced

Circuits in a camera combine thousands of separate signals into a complex picture (frame) Each frame is divided electronically into two fields of alternating lines (interlacing) 30 frames recorded per second 60 separate fields created When played on television your brain “sees” them as continuously moving scene

Transmission Signals sent to antenna Amplified and modulated before transmitted via antenna, satellite or cable Higher frequencies Channel selector on TV receiver tunes in frequency of channel Converts to electrical signals Video and audio signals separated Audio sent to speaker and converted to sound Video sent to display unit (CRT – Cathode Ray Tube)

The Television Receiver Screen is flat part of CRT Covered in red, green, and blue phosphors Covered in red, green, and blue phosphors Phosphors emit light when given energy Pixel – each dot of light Pixels arranged in patterns or rows to make mage Pixels arranged in patterns or rows to make mage 3 electron guns move behind screen emitting beams that excite the phosphors to make them glow

Digital Television Federal Communications Commission (FCC) has mandated switch from analog to digital Digital Television Set (DTV) required to receive broadcasts manipulate video images Store images and sounds Electronically search for programs of interest

High Definition Television (HDTV) Cinema quality video CD quality sound Higher aspect ration than conventional television Conventional 4:3 Conventional 4:3 HDTV16:9 HDTV16:9

Advances in Electronic Communication RFID Technology Radio Frequency Identification Radio Frequency Identification Wireless system that can be used to track goods or vehicles Wireless system that can be used to track goods or vehicles RFID tag contains microprocessor and antenna Radio-emitting scanner or tranceiver Reducing EMI Any device with an electronic circuit emits some electromagnetic radiation Any device with an electronic circuit emits some electromagnetic radiation Electromagnetic Interference Electromagnetic Interference