Communication Technology

Transcription

1 What is communication technology? Communication technology allows people to store, transmit, receive, and manipulate information. ICT ( Information and Communication Technology) is combining telephone lines, wireless, computers, software, and audio-visual systems to achieve communication. What are the key steps in applying communication technology? Encode information into a digital signal Generate/transmit signal Receive signal Decode information from signal to understand the signal

2 What is a signal? What are 4 ways to transmit signals? A signal is what carries information. 4 ways to transmit signals: Electrical - transmitted as voltage and/or current through copper wires Light - transmitted as light pulses through fiberoptic cables, which are flexible glass tubes Light - transmitted through our atmosphere or in space (TV, radio signals) Sound transmitted as sound waves generated by speakers or voices What is sound? Sound is a energy transmitted through matter gases, liquids, solids, and plasma. Plasma is a state of matter where the atoms are charged (not neutral). Sound cannot travel through empty space. Light can!

3 What is light? Light is mostly created by vibrating electric charges (usually vibrating electrons). There is light we can see, and there is light we can t see but detect with instruments. The main difference between light waves is their frequency and energy. Light is classified using the Electromagnetic Spectrum. What is the Electromagnetic Spectrum? The Electromagnetic Spectrum is a way of classifying different types of light.

4 How do we use various types of light to in our technologies? Radio: Your radio receives radio waves emitted by radio stations. Radio waves are also emitted by stars and gases in space. Microwave: Microwave radiation heats only water, which then conducts the heat to the rest of the food. Microwaves are also received by astronomers to learn the origins of the universe. Infrared (Heat radiation): Night vision goggles pick up the infrared light emitted by our skin and objects with heat. In space, infrared light helps us map the dust between stars. UV light at crime scenes Visible: Our eyes detect visible light. Fireflies, light bulbs, and stars all emit visible light. Ultraviolet: UV light sources can reveal blood, seminal fluid, saliva and urine stains. X-ray: A dentist uses X-rays to image your teeth, and airport security uses them to see through your bag. Gamma ray: Doctors use gamma-ray imaging to see inside your body.

5 What are some common technologies that use radio waves? Cell phones Remote controlled model airplanes Garage door openers GPS receiver units (Global Positions System) Bluetooth devices What is wifi? Wifi (or Wi-Fi) is a wireless network that allows receivers to get information. Wifi is a technology that uses radio waves to provide high speed Internet and network connections

6 Draw a communication diagram of a typical Wi-Fi network call. Label where the signal is electrical vs. light (radio wave).

7 What is a digital or discrete signal? A digital signal is discrete - made up of separate packets of information, called bits or bytes You can create a digital signal by turning voltage, sound, or light on and off. A graph of a digital signal looks like packets, lasting for different amounts of time: Signal values can only be 0 = off and 1 = on What is a analog signal? An analog signal is numbers that can have all kinds of values within a certain range (not transmitted in discrete packets of 0 s and 1 s). Examples of analog signals: Video recordings Audio recordings Scanned images A graph of an analog signal looks like a continuous wave:

8 When you transmit Morse Code via a telegraph, how do you encode the information? You tap the switch, which produces electrical pulses. Light signals were used to communicate with ships by rapidly opening/closing the shutters from the light source. Is this form of communication discrete or analog? Closing the shutters is off. Opening the shutters is on. On / off signals are digital, or discrete, signals.

9 For the telephone, what parts of the system are the encoder and the decoder? Encoder Diaphragm in the mouthpiece. When you speak into the mouthpiece, the diaphragm vibrates and converts vibrations to analog electrical currents. Decoder Diaphragm in the receiver vibrates in response to received electrical signals. Diaphragm vibrations vibrate the air and become sound waves we can hear. diaphragm - thin material Describe how information is transmitted in car keyless entry system. Finger presses button on remote to send a signal to the encoder. Encoder in the remote changes the electrical signal to an infrared signal (light), which is sent to the receiver. Decoder in the car converts the received electrical signal to either lock or unlock the car door. The destination of the final electrical signal is to either lock or unlock the door.

10 Is it possible to convert analog signals to digital signals? Yes, it is possible to convert analog signals to digital signals, but some information will be lost. Examples: During the CD revolution, many analog vinyl recordings were converted to digital format stored on CD s, and then MP3s. VHS recordings are analog. However, many were converted to digital format and stored on DVDs. What is a binary signal or binary data? Number bi = two binary = can only have 2 values Binary information is encoded using only 2 values: 0 or off and 1 or on. A bit is a 0 or a 1. All numbers and alphabet letters can be represented with unique sequences of 0 s and 1 s.

11 What is binary code? Binary code is used to represent number and letters using only 0 s and 1 s. Binary code is used to store digital data on computers and other electronic devices. What are the advantages and disadvantages of analog vs. digital systems?

12 What is a fiber-optic cable? Fiber-optic cables are used to transmit light pulses over long distances. Fiber-optics transmit digital signals. Fiber-optic cables are an alternative to copper wires transmitting electricity, which reduce ( degrade ) the quality of signals over long distances. How are digital light signals transmitted through long fiber-optic cables? The materials used in the fiber-optic cables help light travel long distances. On-off laser light pulses enter the optical core, and are reflected from the cladding, which surrounds the core. The materials of the cladding and core cause the light to be reflected back into the core (and not leave).

13 What are the advantages and disadvantages of fiberoptics, compared to copper wires? Fiber-optics transmit digital light signals. Copper wires transmit digital and analog electrical signals. Because electrical wires create magnetic fields, these interfere with the signal produce noise. Advantages of Fiber-Optics Disadvantages of Fiber-Optics Data can be transmitted over long distances without losing information Not affected by temperature (Copper resistance is affected by temperature) Expensive to install More fragile than wire Bundles of fiber-optic cables Not affected by noise, which is true for electrical signals transmitted by copper wires Thinner and lighter than metal wires Difficult to splice (put together) Data can be transmitted digitally, so almost not information is lost Flexible - Light data can be transmitted along a curved path Bundles of copper cables

14 What is the scientific principle behind how fiber-optic cables work? Fiber-optics work based on total internal reflection! Total internal reflection When light goes from more dense to less dense material, part of the light is always reflected. If the light strikes the boundary at a large enough angle, ALL of the light is reflected back to the denser material (cladding). Air Transmitted ray At critical angle, light skims the surface At more than critical angle, no light leaves Cladding Reflected ray Total internal reflection

15 Provide examples of technologies that store information. Computer hard drive Flash drive (USB drive) CD, DVD etched by a laser MP3 device Smart phone What is a laser? A laser technology generates an intense beam of light. The light is coherent stays focused. The light is monochromatic one color

16 What is examples of laser applications. Drilling, cutting Aligning things Recording and playing CDs and DVDs Medical used to cut during surgery What is a laser? A laser technology generates an intense beam of light. The light is coherent stays focused. The light is monochromatic one color