Type your first name and ID number and click on the search button.
Your other names will be displayed. Enter your mobile number starting 254 and remember to omit the zero. Your mobile number will be your user name and your ID number the password.
Click on create to complete the account creation.
Proceed to log in to the RSL portal.
Setting Your Company Pin
The first step is to make sure you set your company pin. Click on the set pin option on the left-hand side. Input your Company’s KRA pin and submit.
Attaching Your Vehicle on the Portal
The next step is to attach a vehicle that you are applying for a license for. Click on the attach vehicle option. Enter the vehicle registration number or chassis number and click on the search button. If the vehicle is found, indicate the sitting capacity. Click on submit.
Applying for the Road License
Click on my vehicles on the left hand side.
A list of your vehicles will be displayed.
On the one you are applying for, click on apply RSL.
Fill in all the areas with an asterisk.
Click next and proceed to make payment.
After your payment is successful, submit the form.
Road Service License Application Online
What to do After Submitting the Application
After submitting your Road License application, the next stage is to keep on checking the progress. On the right-hand side, you will be able to see the progress of your application.
In case your application is rejected, click on edit RSL to see the reason why it was rejected. Make requested amendments and submit.
Once the RSL License is issued, you print it online. You can use available apps to verify your license.
This article discusses different transmission media in computer networks. A transmission media is a channel through which information flows in a network.
In every network, the transmission media carries data in the form of electrical, light or radio wave signals.
On any network, the various entities must communicate through some form of media. Transmission media enable computers to send and receive messages.
There are Two Broad Categories of Transmission Media Namely:
The bounded or the guided media.
The unbounded or unguided media. (Boundless Media)
The Bounded Media
In bounded transmission media, the signal is contained inside a physical media. There are three common types of bounded media namely:-
Coaxial cable
Twisted pair cable
Fibre optic cable
1. The Coaxial Cable Transmission Media
The coaxial cable consists of a solid or stranded copper core (a central conducting core). This core is surrounded by a dielectric (special insulator), a braided or woven copper mesh shielding layer (which is connected to signal ground and absorbs Electromagnetic Interference-EMI).
And finally, a protective outer covering (insulating jacket). All these layers are concentric around a common axis thus the name coaxial.
Surrounding the core is a dielectric insulating layer that separates it from the wire mesh. The braided wire mesh acts as a ground and protects the core from electrical noise and crosstalk. (Crosstalk is signal overflow from an adjacent wire).
Coaxial cable is largely immune to electrical interference and can carry data at higher rates over long distances than twisted pair cable.
The conducting core and the wire mesh must always be kept separate from each other. If they touch, the cable will experience a short, and noise or stray signals on the mesh will flow onto the copper wire.
An electrical short occurs when any two conducting wires or a conducting wire and a ground come into contact with each other. This contact causes a direct flow of current (or data) in an unintended path.
In the case of household electrical wiring, a short will cause sparking and the blowing of a fuse or circuit breaker. With electronic devices that use low voltages, the result is not as dramatic and is often undetectable.
These low-voltage shorts generally cause the failure of a device; and the short, in turn, destroys the data.
A non-conducting outer shield – usually made of rubber, Teflon, or plastic – surrounds the entire cable.
The coaxial cable is more resistant to interference and attenuation than twisted-pair cabling.
It transmits voice, video, and data.
A Coaxial Cable Diagram
Types of Coaxial Cable
There are two types of coaxial cable:
Thin (thinnet) cable
Thick (thicknet) cable
Thinnet Cable / 10Base2 Ethernet
10 refer to the rate of data transfer. It transfers data at the rate of 10Mbps (Megabits per second)
2 refer to distance allowed between computers it should be no more than 2 meters.
Thinnetcable is a flexible coaxial cable about 0.64 centimetres (0.25 inches) thick. Because this type of coaxial cable is flexible and easy to work with, it can be used in almost any type of network installation.
Thinnet coaxial cable can carry a signal for a distance of up to approximately 185 meters (about 607 feet) before the signal starts to suffer from attenuation. A maximum of 30 workstations is allowed per trunk and the distance between them should be a maximum of 2 meters.
Cable manufacturers have agreed upon specific designations for different types of cable. (Table 1.0 lists cable types and descriptions.) Thinnet is included in a group referred to as the RG-58 family (Radio Grade) and has 50ohm impedance.
Impedance is the resistance, measured in ohms, to the alternating current that flows in a wire. The principal distinguishing feature of the RG-58 family is the centre core of copper.
Coaxial Cable Types
Type
Ohms
AWG
Conductor
Description
RG-6
75
18
Solid copper
Used in cable network to provide cable Internet service and cable TV over long distances.
RG-8
50
10
Solid copper
Used in the earliest computer networks. This cable was used as the backbone cable in the bus topology. In Ethernet standards, this cable is documented as the 10base5 Thicknet cable.
RG-58
50
24
Several thin strands of copper
This cable is thinner, easier to handle and install than the RG-8 cable. This cable was used to connect a system with the backbone cable. In Ethernet standards, this cable is documented as the 10base2 Thinnet cable.
RG-59
75
20 – 22
Solid copper
Used in cable networks to provide short-distance service.
Coaxial Cable Types
Thicknet Cable / 10Base5 Ethernet
10 refer to the rate of data transfer. It transfers data at the rate of 10Mbps (Megabits per second)
5 refer to distance between computers it should be no more than 5 meters.
A maximum of 100 workstations is allowed per trunk and the distance between should be a maximum of 5 meters.
Thicknet cable is a relatively rigid coaxial cable about 1.27 centimetres (0.5 inches) in diameter. Thicknet cable is sometimes referred to as Standard Ethernet because it was the first type of cable used with the popular network architecture Ethernet. A Thicknet cable’s copper core is thicker than a thinnet cable core.
The thicker the copper core, the farther the cable can carry signals. This means that thicknet can carry signals farther than thinnet cable. A Thicknet cable can carry a signal for 500 meters (about 1640 feet). Therefore, because of thicknet’s ability to support data transfer over longer distances, it is sometimes used as a backbone to connect several smaller thinnet-based networks.
2. The Twisted-Pair Cable
It consists of two insulated strands of copper wire twisted around each other. Several twisted-pair wires are often grouped and enclosed in a protective sheath to form a cable. The total number of pairs in a cable varies. The twisting cancels out electrical noise from adjacent pairs (cross talk) and other sources such as motors, relays, and transformers.
It consists of two insulated strands of copper wire twisted around each other.
They make use of RJ-45 telephone-type connectors (larger than telephone and consists of eight wires vs. Telephone’s 4 wires).
Generally inexpensive.
Easy to install.
Twisted Pair Cable Types
Unshielded twisted pair
Shielded twisted pair
The Unshielded Twisted Pair (UTP) or (10baset)
UTP, using the 10BaseT specification, is the most popular type of twisted-pair cable and is fast becoming the most popular LAN cabling. These pairs are typically colour-coded to distinguish them. The maximum cable length segment is 100 meters, about 328 feet.
The 568A Commercial Building Wiring Standard of the Electronic Industries Association and the Telecommunications Industries Association (EIA/TIA) specifies the type of UTP cable that is to be used in a variety of building and wiring situations.
The objective is to ensure the consistency of products for customers. These standards include six categories of UTP. The higher the grades number the more immune to the interference and the faster it can accurately transmit data, the categories are as follows:-
Categories of UTP cable are as follows:
Category 1 – Used for telephone communications. Not suitable for transmitting data.
Category 2 – Capable of transmitting data at speeds up to 4 megabits per second (Mbps).
Category 3 – Used in 10BASE-T networks. Can transmit data at speeds up to 10 Mbps.
Category 4 – Used in Token Ring networks. Can transmit data at speeds up to 16 Mbps.
Category 5 – Can transmit data at speeds up to 100 Mbps.
Category 5e – Used in networks running at speeds up to 1000 Mbps (1 gigabit per second [Gbps]).
Category 6 – Typically, Category 6 cable consists of four pairs of 24 American Wire Gauge (AWG) copper wires. Category 6 cable is currently the fastest standard for UTP.
Advantages of UTP Cable
Less vulnerable to network failures
UTP cable is the least costly of any cable type.
Drawbacks of UTP Transmission Media
A network using UTP cables requires the distribution of hubs.
It requires more cabling.
UTP is particularly susceptible to crosstalk, which is when signals from one line get mixed up with signals from another.
Easily tapped (because there is no shielding).
100 meters is the maximum distance so attenuation is the biggest problem while using UTP cables.
Shielded Twisted Pair (STP)
Uses a woven copper braid jacket and a higher quality protective jacket. Also uses foil wrap between and around the wire pairs.
Much less susceptible to interference and supports higher transmission rates than UTP.
Shielding makes it somewhat harder to install.
It has got the same 100-meter limit as UTP.
It is harder to tap.
Used in AppleTalk and Token Ring networks
Shielded Twisted Pair Cable
3. Optical Media
Fibre Optic Cable (100 Base F)
An optic fibre cable consists of an extremely thin cylinder of glass called the core that is surrounded by a concentric layer of glass called a cladding. Optical fibre carries digital signals in the form of modulated pulses of light along a flexible glass tube. It does not use electricity, except to power the transmitting and receiving circuitry at either end.
The outer jacket is for protection while the cladding is used to reflect light signals into the waveguide.
The center conductor of a fiber-optic cable is a fiber that consists of highly refined glass or plastic designed to transmit light signals with little loss. A glass core supports a longer cabling distance, but a plastic core is typically easier to work with.
Fiber Optic Cable
The fibre is coated with a cladding or a gel that reflects signals into the fibre to reduce signal loss. A plastic sheath protects the fibre.
Unlike the other two types of cables, fibre optic cables do not leak signals and are immune to electromagnetic interference. They support greater bandwidth and can transmit data up to a maximum of 2km without the need for repeaters to regenerate the signals. However, they are expensive to buy and install.
The fibre optic strands transfer light in a single direction at a time. Hence 2 strands are placed in each cable to allow simultaneous transmission and reception at the same time.
A fibre-optic system is similar to the copper wire system that fibre-optics is replacing. The difference is that fibre-optics use light pulses to transmit information down fibre lines instead of using electronic pulses to transmit information down copper lines.
Looking at the components in a fibre-optic chain will give a better understanding of how the system works in conjunction with wire-based systems.
At one end of the system is a transmitter. This is the place of origin for information coming onto fibre-optic lines. The transmitter accepts coded electronic pulse information coming from copper wire. It then processes and translates that information into equivalently coded light pulses.
A light-emitting diode (LED) or an injection-laser diode (ILD) can be used for generating light pulses. Using a lens, the light pulses are funnelled into the fibre-optic medium where they transmit themselves down the line.
Light pulses move easily down the fibre-optic line because of a principle known as total internal reflection. “This principle of total internal reflection states that when the angle of incidence exceeds a critical value, light cannot get out of the glass; instead, the light bounces back in”.
When this principle is applied to the construction of the fibre-optic strand, it is possible to transmit information down fibre lines in the form of light pulses.
There are Two Types of Fiber Optic Cables
Single /mono mode
It sets transmissions along a single path like a flashlight. Laser diodes are used to create light signals. The beam is so intense that the single-mode can carry data for a longer distance. It also supports higher speeds and is more expensive. It can extend up to 3 km.
Single-Mode Fiber has a narrow core (eight microns or less), and the index of refraction between the core and the cladding changes less than it does for multimode fibres. The light thus travels parallel to the axis, creating little pulse dispersion.
The Multi-Mode Fiber
Light Emitting Diodes (LEDs) are used to create light signals for multimode. The many wavelengths of light source take multiple light paths along with the fibre and as a result, the light pulses received on the other end are more blurred than it would be produced by mono mode system. Multi-mode signals can extend up to 2km.
Received light pulses are detected and converted to electrical pulses using light sensitive diodes.
Comparison between single mode and multimode fiber- Source
The fiber Optic cable Connectors
There are two types of connectors commonly used with optical fibre. The SC is the most popular in LAN networking.
Advantages of Using the Fiber Optic Cable
It supports high data rates: – can transmit between 100 Mbps to 2 Gbps.
Greater resistance to electromagnetic noise such as radios, motors or other nearby cables.
It’s light and occupies very little space.
It has good data security because cable can’t be tapped and data stolen.
It supports multiple data i.e. data, voice and video.
It can stretch up to 2000m without the need for a repeater.
Disadvantages of Using the Fiber Optic Cable
It’s fragile because of glass
It’s expensive
It requires skilled and trained engineers.
The Unbounded Transmission Media
It is also referred to as Wireless transmission media. No physical medium is required for the transmission of electromagnetic signals.
The wireless environment is an often appropriate, and sometimes necessary, networking option. Today, manufacturers are offering more products at attractive prices that, in turn, will mean increased sales and demand in the future. As demand increases, the wireless environment will grow and improve.
The phrase “wireless environment” is misleading because it implies a network completely free of cabling. In most cases, this is not true. Most wireless networks actually consist of wireless components communicating with a network that uses the cabling discussed earlier in this chapter in a mixed-component network called a hybrid network.
Presently, you can subdivide wireless networking technology into three basic types corresponding to three basic networking scenarios:
Local area networks (LANs). Occasionally you will see a fully wireless LAN, but more typically one or more wireless machines function as members of a cable-based LAN.
Extended local networks. A wireless connection serves as a backbone between two LANs. For instance, a company with office networks in two nearby but separate buildings could connect those networks using a wireless bridge.
Mobile computing. A mobile machine connects to the home network using cellular or satellite technology.
Wireless Network Capabilities
Wireless networks are attracting attention because wireless components can:
Provide temporary connections to an existing, cabled network.
Help provide backup to an existing network.
Provide some degree of portability.
Extend networks beyond the limits of physical connectivity.
Uses of Wireless Transmission Media
They can be useful for;-
Busy areas, such as lobbies and reception areas.
People who are constantly moving, such as doctors and nurses in hospitals.
Isolated areas and buildings.
Departments where physical settings changes frequently and unpredictably.
Structures, such as historic buildings, for which cabling presents challenges.
Wireless Communications with LANs
It is often advantageous for a network to include some wireless nodes. Typically, though, the wireless nodes are part of what is otherwise a traditional, cable-based network.
An access point is a stationary transceiver connected to the cable-based LAN that enables the cordless PC to communicate with the network. The access point acts as a conduit for the wireless PC. The process is initiated when the wireless PC sends a signal to the access point; from there, the signal reaches the network.
Wireless LANs use five techniques for transmitting data:
Infrared transmission.
Laser transmission.
Narrowband (single-frequency) radio transmission.
Spread-spectrum radio transmission.
Microwaves.
INFRARED: All infrared wireless networks operate by using an infrared light beam to carry the data between devices. These systems need to generate very strong signals because weak transmission signals are susceptible to interference from light sources such as windows and the signal cannot travel through objects.
LEDs are used to transmit signals or data between devices and photoreceptor diodes are used to receive data on the other side. Infrared signals are in a very high-frequency range hence they have a good thro’ put. Infrared is just below the visible range of light between 100 GHz and 1000 THz.
There are four types of infrared networks:
Line-of-sight networks: – Data is transmitted only if the transmitter and the receiver have a clear line of sight between them.
Scatter infrared networks: – Broadcasted signals bounce off walls and ceilings and eventually hit the receiver.
Reflective networks: – Optical receiver situated near the computer transmits towards a common location which then direct transmission to the appropriate computer.
Broadband optical telepoint: – This infrared wireless LAN provides broadband services and is capable of handling high-quality multimedia requirements that can match those provided by a cabled network.
LASER: High-powered laser transmitters can transmit data for several thousand yards when line-of-sight communication is possible. Laser technology is similar to infrared technology in that it requires a direct line of sight, and any person or object that breaks the laser beam will block the transmission.
NARROWBAND (SINGLE-FREQUENCY) RADIO TRANSMISSION: This approach is similar to broadcasting from a radio station. The user tunes both the transmitter and the receiver to a certain frequency. This does not require line-of-sight focusing because the broadcast range is 3000 meters (9842 feet). A transmitter generates an electromagnetic field whose size varies at a set frequency. This field spreads outward as an electromagnetic wave, which is detected at a distance by a receiver tuned to respond to the selected frequency only.
SPREAD-SPECTRUM RADIO TRANSMISSION: – Spread-spectrum radio broadcasts signals over a range of frequencies. This helps it avoid narrowband communication problems.
The available frequencies are divided into channels, known as hops, which are comparable to one leg of a journey that includes intervening stops between the starting point and the destination.
The spread-spectrum adapters tune in to a specific hop for a predetermined length of time, after which they switch to a different hop. A hopping sequence determines the timing. The computers in the network are all synchronized to the hop timing.
This type of signalling provides some built-in security in that the frequency-hopping algorithm of the network would have to be known to tap into the data stream.
To further enhance security and to keep unauthorized users from listening in to the broadcast, the sender and the receiver can encrypt the transmission.
Spread-spectrum radio technology provides for a truly wireless network. For example, two or more computers equipped with spread-spectrum network adapters and an operating system with built-in networking capability can act as a peer-to-peer network with no connecting cables. In addition, such a wireless network can be tied into an existing network by adding an appropriate interface to one of the computers on that network.
MICROWAVES: – Microwave systems are a good choice for interconnecting buildings in small, short-distance systems such as those on campus or in an industrial park.
Microwave transmission is currently the most widely used long-distance transmission method. It is excellent for communicating between two line-of-sight points such as:
Satellite-to-ground links.
Between two buildings.
Across large, flat, open areas, such as bodies of water or deserts.
Two radio transceivers: one to generate (transmitting station) and one to receive (receiving station) the broadcast.
Two directional antennas pointed at each other to implement communication of the signals broadcast by the transceivers. These antennas are often installed on towers to give them more range and to raise them above anything that might block their signals.
Microwave communication falls into two categories:-
Terrestrial Microwave
Satellite microwave.
i) TERRESTRIAL MICROWAVE: – It uses earth-based transmitters and receivers in the low GHz range of frequency (4-6GHz or 21-23GHz). Speed is often 1-10Mbps. The signal is normally encrypted for privacy.
Communication is through the line of sight and cannot go round corners or through buildings. Line-of-sight means that the transmitter’s beam is focused directly on the receiver. Microwave dishes (parabolic antennas) are seen on top of tall buildings.
ii) SATELLITE MICROWAVE: – It uses a communication satellite that operates in geosynchronous orbit (rotate around the earth) at 22300 miles 36000km above the earth’s surface which is an altitude that will cause it to stay in a fixed position relative to the rotation of the earth.
A geosynchronous satellite must orbit at 22,300 miles altitude and it must be over the earth’s equator. As a result, there are a limited number of slots available for satellites. The allocation of these slots is carefully regulated by an international governing body.
