Principles of Telecommunications Technology

Chapter 2

Objectives

In this chapter, you will learn to: Describe the principles of electricity that underlie all

telecommunications signaling Explain the concepts of current and voltage as they apply

to telecommunications technology Describe the components on an integrated circuit Explain the difference between analog and digital

transmission Use binary encoding to represent decimal numbers Describe various electricity and data transmission

measurements

Atomic Charges

Charge - the characteristic of a material that enables it to exert force on another material.

Neutrons - found at the center of an atom, possess no charge and are said to be neutral.

Protons - found at the center of an atom along with neutrons, carry a positive charge.

Electrons - orbit the center of an atom and carry a negative charge

Atomic Charges

Static Electricity

Static electricity - the release of an accumulated charge in some material or object.

Because the charges inherent in electrons and protons are bound to balance each other through static electricity, these charges are also called electrostatic charges.

Electric Current

Electric current - the controlled movement of an electrical charge (or electrons) along the atoms of a conductor.

Circuit - a closed connection between an electric source (such as a battery) and a load (such as a lamp) over which current may flow.

Signal - occurs when current manipulated to transmit information.

Electric Current

Voltage - the pressure that the electric current exerts on its conductor is known. It is commonly equated to the strength of the electric current, and is measured in volts

Amperes - the amount of current (or charge flowing through a wire each second ) is measured in amperes, abbreviated as amps.

Resistance - a material’s opposition to electric current.

Electric Current

Conductors and Insulators

Conductor - a material over which electric current readily flows.

Grounding - the use of a conductor (such as a wire) to divert unused or potentially harmful charges to an insulator, where they will be stopped or absorbed.

Insulators - materials that do not allow electric current to flow easily.

Semiconductor - conducts electricity better than an insulator, but not as well as a conductor.

Conductors and Insulators

Resistance

Calculating Voltage, Amps, and Resistance with Ohm’s Law

Direct and Alternating Current

Direct current (DC) - an electrical charge flows steadily in one direction over the conductor.

Direct and Alternating Current

Alternating current (AC) - the electrical charge flows in one direction first, then in the opposite direction, then back in the first direction, and so on, in an alternating fashion over the conductor.

Direct and Alternating Current

Direct and Alternating Current

Capacitance

The ability for an electric circuit or component to accumulate or store a charge.

Capacitance is measured in Farads (abbreviated as F), a unit named after English chemist and physicist Michael Faraday, who experimented with electricity in the early 1800s.

Capacitor - a device that stores electrical charge (as the tank stores water).

Capacitance

Capacitance

Capacitance

Capacitance

Inductance

Inductance

Inductance

Inductance

Inductance

Inductance

Electrical Power

Electrical Power

IQ TEST 1

1. A(n) _____ is the characteristic of a material that enables it to exert force on another material.

Answer: charge  2. _____ is the release of an accumulated charge in some material or object.

Answer: Static electricity 3. A(n) _____ is a closed connection between an electric source and a load

over which current may flow. Answer: circuit

 4. A material over which electric current readily flows is known as a(n)

_____.Answer: conductor

 5. _____ is a material’s opposition to electric current.

Answer: Resistance

Measuring Electricity

Measuring Electricity

Measuring Electricity

Passive Electronic Devices

Passive device - a component that contributes no power gain to a circuit.

Resistor - a component inserted into a circuit to provide a specific amount of resistance

Diodes

Diodes

Transistors

Integrated Circuits

Circuits that combine the conductor and the attached components of a circuit in one small unit.

IQ TEST 2

1. A(n) _____ is a component that contributes no power gain to a circuit. Answer: passive device

 2. A(n) _____ is an electronic component that is capable of controlling voltages or currents it receives.

Answer: active device 3. A(n) _____ is an electronic component that allows current to flow in only one direction.

Answer: diode 4. A(n) _____ is a device that can start and stop current on a circuit.

Answer: switch

Analog Transmission

Analog - electromagnetic signals that continuously vary in their strength and speed.

Transmission Flaws

Noise - unwanted interference from external sources, which can degrade or distort a signal.

Attenuation - the loss of a signal’s strength as it travels away from its source.

Amplifier - an electronic device that increases the voltage, or power, of the signals.

Regeneration - when digital signals are repeated, they are actually retransmitted in their original, pure form, without any noise.

Repeater - a device that regenerates a digital signal.

Transmission Flaws

Transmission Flaws

Encoding and the Numbering System

Encoding - the process of modifying data so that it can be interpreted by the receiver.

Methods for encoding data include: The Decimal System The Binary System Hexadecimal System EBCDIC ASCII UNICODE

Measuring Data

Throughput and Bandwidth

Throughput - the amount of data that a communications channel can carry during a given period of time. The physical nature of every communications channel

determines its potential throughput.

Bandwidth - a measure of the difference between the highest and lowest frequencies that a media can transmit.

IQ TEST 3

 1. A system that uses 1s and 0s to transmit information is known as a(n) _____.

Answer: binary 2. _____ is unwanted interference from external sources which can degrade or distort a signal.

Answer: Noise 3. The loss of a signal’s strength as it travels away from its source is called _____.

Answer: attenuation 4. Analog signals pass through a(n) _____, an electronic device that increases the voltage, or power, of the signals.

Answer: amplifier

Data Communications and Computer Networks: A Business User's Approach, Seventh Edition 48

Data vs Signal

• Data are entities that convey meaning (computer files, music on CD, results from a blood gas analysis machine)

• Signals are the electric or electromagnetic encoding of data (telephone conversation, web page download)

• Computer networks and data/voice communication systems transmit signals

• Data and signals can be analog or digital

Data Communications and Computer Networks: A Business User's Approach, Seventh Edition 49

Four combinations of data and signals

Summary

Electricity may exist as either static electricity, the imbalance of charges, or as current electricity, the flow of charge along a conductor.

The three main characteristics of a circuit are voltage, current, and resistance. If two of these characteristics are known, the third can be calculated using Ohm’s Law.

Electronic devices may be active or passive. Examples of passive devices are capacitors and inductors. Examples of active devices are transistors and diodes.