My Tech Tips

In my previous article I wrote about Understanding Computer Communications (Read it here). I covered the history of communication and how today’s computers communicate with the user, each other and the outside world. I focused mostly on the use of wires and cables for the transmission of data. But the common terminology for exchanging information with computers is 'Networking'. Rather confusingly, networking can be both wired or wire-less. This article explains all about network connections. Here are some terms that I will cover: Local Area and Wide Area Networks (LANs and WANs), Ethernet, Wi-Fi, Bluetooth, Mobile, Terrestrial, and Satellite.
 
Wired Networks (LANs and WANs)
When we talk of a network we refer to an arrangement whereby one or more computers can be linked together to exchange data. This can be within one’s home or office (the Local Area Network or LAN) or between different buildings and departments of a business (the Wide Area Network or WAN [sometimes called a Corporate Network]). Of course, we have already met one network called the Internet(work) which is really a global network for information exchange.
 
Local Area Networks (LANs) can be established by connecting the computer(s) within the home or office using wires or wireless signals.  When we use wires we use a form of cabling called Ethernet. Ethernet cables can be any length and there is usually little or no degradation of signal over reasonable distances. Ethernet cables are about the thickness of a normal electrical appliance cable. They consist of a number of separate wires which are bundled together and encased in a plastic outer sheath. Typically they run along skirting boards and although they can be visually distracting they can blend in well especially if you choose an appropriate colour cable. Most people will be familiar with this ethernet cable since one is always included in the box when you take delivery of an internet hub or router. Here is a picture of an Ethernet Cable. 

​You will notice that there is a different type of plug at each end of the cable and this demands a special socket or port to connect to at its destination. For the technically curious this plug is called an RJ45 (which stands for Registered Jack 45).The ‘destination’ it plugs into might be the back of your computer, a port on your internet hub/router, or even a junction box for sharing the network between more than one device. Here is a picture of the LAN socket or port with its cable. Look for it on the back of your computer or hub.

​If you ever have the luxury of having a new house built it makes sense to get the whole house cabled for ethernet with appropriate sockets in each room. This way, the cabling can be hidden behind plasterwork or walls in just the same way that a ring main electric cable is laid out and hidden when building a house. Here is a picture of a typical face plate that might be built into a wall to provide a network connection point.  Increasingly these are being combined with three pin plug sockets and USB charging points. The ethernet socket usually sits behind a small shutter that has to be lifted up to insert the connecting cable. This shutter prevents the ingress of dirt and dust. You will be familiar with these shutters on telephone points. Interestingly, the standard telephone plug is called an RJ11 (Registered Jack 11) and is smaller than the ethernet plug.

​Wide Area Networks (WANs) are where different parts of an organisation are linked together over distances. A business with, for example, a headquarters and a number of regional offices each with its own LAN, might have a WAN that connects all the regional LANs together. Thus regional businesses can operate by themselves over their LAN but communicate data to other regions and to the Head Office by means of the WAN. How these separate LANs are combined is outside the scope of this article but it requires some kind of “junction box” often called an access point. The "highway" for connecting LANs and WANs together is actually the internet. However, the difference is that the LAN/WAN network is private to the organisation and will have safeguards to maintain that privacy. Other organisations that use WANs are Universities, academic institutions, Local Government and Voluntary Services.
 
Wireless Networks
Now let me look at networking without wires - literally Wireless. We have become accustomed to the term Wi-Fi. Knowing that the musical HiFi stands for High Fidelity, it is commonly thought that the Wi-Fi means Wireless Fidelity. This is actually untrue; Wi-Fi doesn’t stand for anything. It is an official trademark of the Wi-Fi Alliance. When looking for a term to describe wireless connectivity they thought that HiFi had a catchy ring to it and imitated it with Wi-Fi.  Note that the correct term is Wi-Fi not WIFI or wifi.
 
All forms of wireless communication require the presence of a transmitter and a receiver. Any device connected to a wireless network has to have the ability to transmit and receive. Depending on the distance between the sender (transmitter) and the device being sent to (receiver) there is often a need for the signal to be boosted on its journey. This is called relay and, like an athletics relay race, has one device in the chain taking hold of the message and carrying (relaying) it to the next recipient and so on.  To understand this concept, think of mobile phones and televisions. The former requires a network of masts (relays) and the latter the presence of large transmitters (relays) usually sited on prominent hilltops.  
 
It is the distance between devices (or between the intermediate relays) that determines the kind of wireless technology to be used.  Here is a brief rundown of the technologies based on distance:
 
Near Field Communication (NFC) This is a common feature of point of sale payment systems using credits/debit cards and mobile phones. The message (card details) are transmitted between the card/phone and the device used by the shop or individual to take the payment.  A receipt message is transmitted back to the card/phone. The maximum distance is about 4cm.
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Bluetooth This technology is used to transmit data at high frequencies over short distances – typically up to 10m but (with higher-powered devices) up to 100m. The technology takes its name from the 10th Century second king of Denmark, King Harald Bluetooth. He was famous for uniting Scandinavia and serves as a metaphor for our uniting computers and devices.  A lesser-known fact is that the blue symbol we use for the Bluetooth icon is actually the initials of Harald Bluetooth in Scandinavian runic script.

Common uses of Bluetooth are for connecting devices such as keyboards, mice and touch pads to their parent computer. Bluetooth is a common feature used in cars for connecting one’s mobile phone to the vehicle’s own computer.  The act of uniting the two devices is called “pairing”.
 
Wi-Fi Perhaps the most regularly-used and recognised form of wireless connection in the home is Wi-Fi. Depending on the inbuilt technology being used and the radio frequency it operates at, Wi-Fi can connect over distances up to 50m indoors. Older devices managed much less. Wi-Fi is typically used for creating a Local Area Network in the home or office. Devices connecting to the network (such as printers, scanners and other computers) do not have to be in line of sight of other devices but have to be within the range of the Wi-Fi transmission frequency.  Where the distance is too much to get a constant signal it is common to use a repeater or extender to act as a relay to other parts of the house.

​​Mobile Communications The next kind of wireless communication is the mobile phone network. Here a more powerful transmitter in the phone or device is able to connect over much greater distances provided that it is within the range of one of the mobile network company’s transmitters (or masts).  Line of sight plays an important part in being able to connect as does the sort of technology being used by the network.  Coming into more regular use is what is called 5G mobile (where 5G stands for 5th Generation). A 5G network is capable of sending signals over much greater distances than earlier generations.  Using the same metaphor of the relay race, mobile network transmitters/masts are situated in a carefully designed geographical spread – each mast counting as a cell which, in conjunction with the other masts in the area creates a cellular network. This is why mobile phones (especially in the US) are called Cell phones.  You will hear an American asking for your “Cell” when he wants your mobile number. Here is a depiction of a mobile network cellular structure (photo courtesy of Rhode & Schwarz):

​The key thing about mobile/cellular networks is that the pathway around the network is switchable – often immediately and without interruption – if one adjacent cell cannot be connected to or is busy. Thus the route a message takes can vary and can be quite circuitous. This gives the network survivability should one cell or group of cells go out of service. The origins of the internet are based on a cell network that was developed in the early 1970s and was intended to be survivable in the event of a major war. The network could carry on working provided a route round the network could be found.
 
Terrestrial Communication  As previously mentioned, Television and Radio programmes are carried across the airwaves by means of transmitting stations. These are much more powerful than mobile phone masts and thus fewer are needed to cover large areas.  The receiver in this instance is the aerial on the roof of your house or in the attic or built in to the television itself. (Joke: Someone was puzzling over a TV set in a shop that said on the box ‘Built In Antenna’. He said to the salesman that he was hoping to get one built in the UK.)
 
Satellite Of course, more and more television programmes are being broadcast by satellite of which Sky is one of the foremost providers. These broadcasts are still wireless even though you can now get cable TV.  Just like terrestrial television, satellite television requires a receiver which is the dish affixed to the outside of the house. Since, like most wireless transmission, line of sight is a necessary factor, the transmitting satellite is what is called geo-stationary, which means that its position remains constant regardless of the rotation of the earth.
 
A Final Word about Line of Sight

In earlier articles I have described the origin of computers and charted their development over the years. I have explained how today’s computers actually work and have provided some guidance about browsers, search engines and how to find information on the internet.  Now I want to look at how we connect to our computing device (which might be a laptop, a desktop, a tablet or a phone) and how that device connects to the outside world and communicates across the internet.

What is communication?
First, however, a few words about the subject of communication. Since time began man has needed to communicate with others – to exchange information. Before speech I imagine that communication was by means of hand gestures but when speech arrived the concept of language evolved. Each language would have been different from others though some might just have been closely related. These days there are known to be over 7000 distinct spoken languages in the world (and each of these can have many regional dialects).
 
But speech has not been the only means of imparting information over the centuries as these pictures indicate:

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A common factor in all of these of course is distance. The greater the distance the less effective the means of communication. Some work over greater distances than others – compare smoke signals and flags. But there is another distinction to make; some forms of communications are visual - relying on seeing something being communicated. Other forms are based on the transmission of sound. But key to all of them is the need to overcome the constraints of distance.

Speech, for example, can travel further if you shout or amplify the sound of your voice. Another technique could be the use of a relay (or repetition). In its simplest form this could be shouting a message to someone who, in turn, relays it to the next person in the chain. Or there could be a visual relay such as sending smoke signals from one hill to another and then having the message sent on further. Over history, early warning systems have utilised fire beacons lit on prominent hills – announcing some event or threat. Keep in mind these concepts of amplification and relay because they form key ingredients of modern-day computer communications.

How does this relate to computer communications?
In my article ‘How do computers actually work?’ (Read it here) I described how early digital computers used some form of electric spark or signal to “instruct” the computer to carry out a particular action. This led to realisation that you could “programme” a computer using a sequence of signals. Programmes are how we communicate with the computer but how do computers communicate with each other and connect to the outside world?  Just as early man sent a stream of smoke signals to convey his message, so computers send a stream of electronic signals in order to communicate. These signals represent numbers and we learnt in the earlier post that the numbers are represented by the use of 1s and 0s in binary arithmetic. There are two issues to examine. First, how the signal passes from one computer to the next and, second, what is the pathway along which that signal travels.
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How does the signal pass from one computer to the next?
We’ve learnt that the passage of signals is sent electronically. But how does this happen? If we think of using the telephone to speak to someone, the sound of our voice goes up and down in a wave.

This wave fluctuates up and down both in the loudness of the voice (amplitude) and its highness or lowness (pitch or frequency). Telephone lines transmit the voice signals on an ever-changing wave. To understand the difference, just ask yourself “Do I speak in 1s and 0s?” No, of course not. But computers do. This is the key difference; our voice signals are analogue (they vary up and down) but computer signals (data) are digital (either 1s or 2s, up or down, on or off). Telephone lines can only handle traffic (voice or data) using fluctuating waves. The microphone part of the phone conveys your voice and the speaker part enables the sound to be heard.
 
With computer data there has to be some way to translate the information from digital 1s and 0s to analogue wave patterns. This translation is called modulation. At one end of the line the signals are modulated and at the receiving end the signals are demodulated. The piece of equipment to do this is called a MODEM (Modulate/Demodulate). Forty years ago, when Personal Computers were starting to appear, we sought ways to join computers up and send messages. Enter the Modem. I remember using a modem into which you inserted the telephone and this enabled signals to be transmitted.  This early modem was called an acoustic coupler. Below is what it looked like and if you click the link underneath you can hear what it sounded like. That noise is the process of turning digital 1s and 0s into sound waves so they can travel over a telephone line.

To hear what it sounded like CLICK

​We still use modems to this day. There is one inside every internet router or hub that sits on your desk. Thankfully they make no noise whatsoever now.
 
But do you remember that, at one time, if you had hooked up your computer to a modem you couldn’t use the telephone to speak to someone on the same line? Fortunately this was overcome by a development called Voice over Data. (NB for those more up-to-date readers. This is not the same as modern Video on Demand (VOD). More sophisticated modems/routers soon enabled the two to work at the same time on the same telephone line. There was an old joke that suggested this was possible because computer bits were heavier than speech and so fell to the bottom of the telephone line. In fact it was because technicians worked out how to split the capacity of the telephone line into a voice section and a data section. Overnight it became possible to speak to someone whilst another member of the family in another room was “on the computer”.
 
What is the pathway along which that signal travels?
Having looked at how signals travel let’s consider the medium over which they move. For the past several decades this has been a simple, telephone copper wire. Even today the copper wire still dominates a lot of the lines to our houses and businesses. Increasingly we are seeing the introduction of Fibre internet. British Telecom (BT) has ownership of all the telephone cabling in this country. Nearly all the main (trunk) networks have now been converted from copper to Fibre. However, this fibre only goes as far as the green cabinet on the corner of your street. This is called FTTC or Fibre to the Cabinet.  The final connection from the cabinet to your house can be either copper (still) or, if you pay more, fibre. The costliest connections have fibre directly into the house or office and are called FTTP or Fibre to the Premises. Even if another broadband provider offers you a service the reality is that they have to rent the trunk cabling from BT.

So what is the difference between copper wire and fibre?  Here are pictures of a standard 5 pair (10 wires) copper telephone cable and, on the right, a multi-strand fibre cable. There can be up to 200 strands of fibre which are usually made of plastic but can be made of glass.