1 / 12

Chapter 4: Electronic and Signals

Chapter 4: Electronic and Signals. Aleksandar Radovanovic University of the Western Cape. Parts of an Atom. nucleus - the center part of the atom, formed by protons and neutrons protons - particles have a positive charge , and along with neutrons, form the nucleus

montana-irwin
Download Presentation

Chapter 4: Electronic and Signals

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 4: Electronic and Signals Aleksandar Radovanovic University of the Western Cape

  2. Parts of an Atom • nucleus - the center part of the atom, formed by protons and neutrons • protons - particles have a positive charge , and along with neutrons, form the nucleus • neutrons - particles have no charge (neutral), and along with protons, form the nucleus • electrons - particles have a negative charge, and orbit the nucleus

  3. Basics of Electricity • Voltage (V): Electrical pressure due to separation of electrical charge.Unit of measurement: Volt • Current (I): Flow of electrons Unit of measurement: Ampere • Resistance (R): Property of material that opposes electrical flow. Unit of measurement: OhmElectrons flow only incircuits that are closed, or complete, loops.

  4. Measuring electricity • A millimeter is a electrical testing tool that can perform measurement of: • voltage • resistance, • continuity (the level of resistance of a path) • Some of the networking related measurements: • CAT 5 cable • terminated coaxial cable • telephone wire • CAT 5 jacks • wall outlets

  5. Analog and Digital • Analog signals: • Continuous, “wave” voltage-versus-time graphs • used in telecommunications for over 100 years • Digital signals: • has discrete, or jumpy, voltage-versus-time graphs • Usually has two voltage levels

  6. Bits on Media • One bit, on an electrical medium, is the electrical signal corresponding to binary 0 or binary 1. • The bit takes a small amount of time to travel (propagate) along the medium. • The time it takes the bit to travel from one end of the medium and back again is referred to as the round trip time, (RTT).

  7. Attenuation • A 1 bit voltage signal loses amplitude as energy passes from the signal to the cable. • Attenuation is the loss of signal strength • Attenuation also happens to optical signals; the optical fiber absorbs and scatters some of the light energy. • One way to fix the problem is to change the medium. A second way is to use a repeater after a certain distance.

  8. Reflection • When voltage pulses, or bits, hit a discontinuity some energy can be reflected. If not carefully controlled, this energy can interfere with later bits. • Can be resolved by ensuring that all networking components are impedance matched. • Reflection occurs with optical signals. Optical signals reflect whenever they hit a discontinuity in the glass fiber, such as when a connector is plugged into a device.

  9. Dispersion, jitter, and latency • Dispersion is when the signal broadens in time. • Timing jitter happens when source and destination clock loose synchronization. • Latency, is a signal delay. To travel a distance, a bit takes at least a small amount of time to get to where it's going. If the bit goes through any devices, the transistors and electronics introduce more latency.

  10. Noise • Noise is unwanted additions to voltage, optical, or electromagnetic signals. • 1. NEXT-A and NEXT-B (near-end crosstalk): when electrical noise on the cable originates from signals on other wires in the cable, this is known as crosstalk.Solution: quality cables and termination. • 2. Thermal noise, due to the random motion of electrons, is unavoidable but usually relatively small compared to our signals. • 3. AC Power/Reference Ground Noise: bad grounding, long wires, faulty electrical devices.Solution: separate LAN power supply. • 4. Electromagnetic interference (EMI), and radio frequency interference (RFI).Solution: shielding and cancellation

  11. Collision • A collision occurs when two bits from two different communicating computers are on a shared-medium at the same time. • In the case of copper media, the voltages of the two binary signals are added, and cause a third voltage level. This voltage variation is not allowed in a binary system, which only understands two voltage levels. The bits are corrupted "destroyed".

  12. Summary • Electricity is based on the ability of electrons of certain types of atoms to separate, or flow. Electricity flows from negative to positive within electrical circuits • The concepts of voltage, current, and resistance, provide a means of measuring electricity which is required to be able to design and manufacture electronic devices. • One bit, on an electrical medium, is the electrical signal corresponding to binary 0 or binary 1. • Six things that can happen to 1 bit: • propagation • attenuation • reflection • noise • timing problems (dispersion, jitter, and latency) • collisions

More Related