For Geeks @nd the not so Geeky

Ethernet Cable

What is an Ethernet Cable

Loosened electrons that do not move and have a negative charge are called static electricity.
If these static electrons have an opportunity to jump to a conductor, this can lead to electrostatic discharge (ESD).

Voltage is sometimes referred to as electromotive force (EMF). Ethernet cables basically allow for the transportation of data along several wires depending on the protocol used.

crossover ethernet cable

Resistance and Impedance in Ethernet Cable Installation

Impedance includes resistance, capacitance, and inductance and is similar to the concept of resistance.
Attenuation is important in relation to networks.

Attenuation refers to the resistance to the flow of electrons and explains why a signal becomes degraded as it travels along the conduit.

Semiconductors are materials that allow the amount of electricity they conduct to be precisely controlled.
Silicon (Si) is the most important semiconductor because it makes the best microscopic-sized electronic circuits.

Current in an Ethernet Cable Network

Electrical current is the flow of charges created when electrons move. In electrical circuits, the current is caused by a flow of free electrons.
When voltage is applied and there is a path for the current, electrons move from the negative terminal along the path to the positive terminal.

The negative terminal repels the electrons and the positive terminal attracts the electrons. The letter I represents current. The unit of measurement for current is Ampere (A). An ampere is defined as the number of charges per second that pass by a point along a path.

Current can be thought of as the amount or volume of electron traffic that flows. Voltage can be thought of as the speed of the electron traffic.
The combination of amperage and voltage equals wattage. Electrical devices such as light bulbs, motors, and computer power supplies are rated in terms of watts. Wattage indicates how much power a device consumes or produces.

It is the current or amperage in an electrical circuit that really does the work. For example, static electricity has such a high voltage that it can jump a gap of an inch or more. However, it has very low amperage and as a result can create a shock but not permanent injury.

The starter motor in an automobile operates at a relatively low 12 volts but requires very high amperage to generate enough energy to turn over the engine.
Lightning has very high voltage and high amperage and can cause severe damage or injury.

Ethernet Lan Cable

Two ways in which current flows are alternating current (AC) and direct current (DC).

The relationship among voltage, resistance, and current is voltage (V) equals current (I) multiplied by resistance (R). In other words, V=I*R. This is Ohm’s law, named after the scientist who explored these issues.

An oscilloscope is an electronic device used to measure electrical signals relative to time.

Power lines carry electricity in the form of AC because it can be delivered efficiently over large distances. DC can be found in flashlight batteries, car batteries, and as power for the microchips on the motherboard of a computer, where it only needs to go a short distance.

Make Your Own Ethernet Cable – Ethernet Cable Wiring Specifications

10BASE-T Baseband(digital) Twisted Pair
10BASE5 Baseband(digital) Thicknet 500m
10BASE2 Baseband(digital) Thinnet 200m(185m)
STP 10-100Mbps 150Ohm cable 100m
UTP SCTP FTP 10-100Mbps) 100Ohm cable 100m

The metallic shielding materials in STP and ScTP need to be grounded at both ends. If improperly grounded or if there are any discontinuities in the entire length of the shielding material, STP and ScTP can become susceptible to major noise problems.

 Ethernet Cable Speeds


Cat3 10Mbps
Cat4 20Mbps
Cat5 100Mbps
Cat5e-7 1Gps


Installing Ethernet Cable – Optical Media

  • The wavelength of the light in optical fiber is either 850 nm, 1310 nm, or 1550 nm.
  • The greater the optical density of a material, the more it slows light down from its speed in a vacuum.
  • The core of the optical fiber has to have a larger index of refraction than the material that surrounds it.
  • The material that surrounds the core of the fiber is called the cladding.
  • The angle of incidence of the light ray is greater than the critical angle for the core and its cladding.


Fiber Optic Ethernet Cable

Single-mode small core less dispersion 3km laser
Multi-mode larger core more dispersion 2km LED
Loose-Tube prevents micro bends lower attenuation
Tight-buffer high impact strength abrasion resistance small size

Wireless Media

802.11 1-2Mbps 2.4Ghz
802.11b 11Mbps 2.4Ghz Wi-Fi
802.11a 54Mbps 5Ghz not backward compliant
802.11g 54Mbps 2.4Ghz backward compatible
  • FHSS – Frequency Hopping Spread Spectrum
  • DSSS – Direct Sequence Spread Spectrum
  • OFDM – Orthogonal Frequency Division Multiplexing

AP cell range is from 91.44 to 152.4 meters. A 20-30% overlap is desirable when roaming between AP’s.

Active scanning causes a probe request to be sent from the wireless node seeking to join the network. The probe request will contain the Service Set Identifier (SSID) of the network it wishes to join.

When an AP with the same SSID is found, the AP will issue a probe response. The authentication and association steps are completed.

Passive scanning nodes listen for beacon management frames (beacons), which are transmitted by the AP (infrastructure mode) or peer nodes (ad hoc). When a node receives a beacon that contains the SSID of the network it is trying to join, an attempt is made to join the network.

Passive scanning is a continuous process and nodes may associate or disassociate with APs as signal strength changes.

Joining a W-Lan

  • SSID match
  • Authenticate
  • Associate

Frame Types

Management Frames

Control Frames

Data Frames

Association request/response frame Request to send(RTS)

Similar to 802.3

Probe request/response frame Clear to send(CTS)
Beacon frame Acknowledgement(ACK)
Authentication frame


  • EAP-MD5 Challenge
  • Lightweight extensible authentication protocol (LEAP)
  • User Authentication
  • Encryption
  • Data Authentication

There is no such thing as a serial Ethernet cable. There exist however serial Ethernet converters which are capable of linking any serial devices via Ethernet.

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