Occupational Health and Safety (OHS) refers to the legislation, policies, procedures and activities that aim to protect the health, safety and welfare of all people at the workplace.

        Every worker has a right to healthy and safe work and to a work environment that enables them to live a socially and economically productive life. Safety practices should be learned early and always adhered when working with any electrical device including personal computers and peripherals.

 The following statements are some safety precautions to take before working with any computer devices:

· Before doing anything, listen to your teacher’s instruction to prevent accidents or any unwanted events that may occur on your workplace.

· Do not work on computer when you are wet because you might get electrocuted.

· Do not remove internal devices of the computer when it is turned on.

· Avoid playing or running while inside the room.

· Always wear personal protective equipments (PPE) like coverall, shoes with rubber sole, anti-static wrist strap, etc.

· Ask for assistance from your teacher when it comes on dealing with computer devices.

· Applying safety measure when handling tools and equipment are necessary to avoid certain damages. The student is further expected to maintain good health, to be neat in personal appearance and to practice safe working procedures at all time with appropriate equipment.

        This lesson will introduce us to the fundamental knowledge of electricity. It will enable student to be equip with the basic knowledge in electricity.

     In direct current (DC), the flow of electric charge is only in one direction. This is the type of electricity is produced by batteries, static, and lightning. A voltage is created, and maybe stored, until it is consumed. When the current flows directly, in one direction. In the circuit, the current flows at a specific, constant voltage (this is oversimplified somewhat but good enough for our needs.) When you use a flashlight, pocket radio, portable CD player or virtually any other type of portable or battery powered device, you are using direct current.

       Most DC circuits are relatively low in voltage; for example, your car's battery is approximately 12V, and that's about as high a DC voltage as most people ever use.

Direct currents flow in one direction only, and are constant in time. Their appearance is that of a straight line which does not vary. They are produced from power sources such as batteries, power supplies and DC generators. Photovoltaic devices such as solar cells also generate DC power. 

   In alternating current (AC, also ac) the movement of electric charge periodically reverses direction. This type of electricity is produced or generated by AC generators commonly from a hydro electric plant. It is the commercial power that we use in homes and offices. Delivered through a power transmission lines. AC current can be reduced through the use of power transformer to suite for its application. It can also be converted to DC for a specific purpose. In the Philippines AC is rated as 220V AC at 60 Hz.

    Alternating currents change direction, flowing first one way and then the other. They are sinusoidal waves, so that they change in time. They are produced from sources such as power supplies and AC generators. In North America, AC is 120 volts and 60 hertz or cycles per second. This means it changes direction 60 times per second. In Europe, it is generally 50 hertz with 220 to 240 volts.

         There are a number of reasons, but one of the most important is that a characteristic of AC is that it is relatively easy to change voltages from one level to another using a transformer, while transformers do not work for DC. This capability allows the companies that generate and distribute electricity to do it in a more efficient manner, by transmitting it at high voltage for long lengths, which reduces energy loss due to the resistance in the transmission wires. Another reason is that it may be easier to mechanically generate alternating current electricity than direct current.

    Sometimes when the problem with a system is not totally apparent and the problem may be intermittent, using a basic common diagnostic procedure may help determine what is wrong. This procedure has a number of steps that, if followed each time, can be of help.

1. Know the facts  

• Educate oneself on all aspects and operation of computer parts.  

• Continuous learning on computer technology. 

2. Use your common sense 

3. Focus on Field Replaceable Units 

• Identify the different types of FRU that can be used for replacement or sub assembly. 

4. Proper assembly and disassembly 

5. Factors Causing Computer Failures and Defects 

People ware  

• Untrained personnel would probably damage programs in PC. Firmware  

• Programs or software burnt in chips may be corrupted. Software  

• Corrupted operating systems would cause the system to fail. Hardware  

• Defective hardware components would lead to computer malfunction.  

• Hardware conflicts and viruses can hinder your computers performance.

Electro static discharge can easily damage sensitive components in your computer. 

Incoming supply from AC outlet must be regulated; power surges can damage computer units. 

        Problem isolation is a detective work in which you need to determine what is out of the ordinary by making detailed observation of what is not working normally and record any information as you proceed. The information you will be able to gather will help diagnose your computer. You need to observe wisely. Look for any abnormalities in the unit, any change in smell or foreign smell, listen to all the sounds, and error codes.

    This section will aid in determining components in your system which are failing. First, most systems have 3 major components; monitor, system unit, and printers. Some have multiple external devices. To troubleshoot, you need to isolate major components which are failing to operate. 

1.       Determine whether or not the power comes on.

2. Check the switch operation with a Digital Volt Meter on the continuity or resistance setting.

3. Check the pins if the corresponding voltage are properly regulated to the motherboard.

4. Replace the power supply unit if defective.

      There are many devices, parts, cords, and connections on a computer, which means that there are many possible problems that could arise. In addition, your computer uses a variety of software, which can also cause problems. However, no matter what the problem is, you can use the following tips to help you find a solution:

· Always check the cables: Many computer problems are related to an issue in the cables and connections. The easiest first step you can take to troubleshoot most problems is to check all related cables and connections.

· Isolate the problem: If possible, try to isolate the problem. For example, if you can't get the cursor to move on the screen, try to determine if the issue is with the mouse. If you have an extra mouse, you can alternate devices to see if the one plugged in is the issue, or use the arrow keys on the keyboard to help determine if the mouse is the source of the problem. When trying to isolate the problem, only make one change at a time.

          Most of the time, problems can be fixed by using simple troubleshooting techniques, such as closing and re-opening the program. It's important to try these simple solutions before resorting to more extreme measures. If the problem still isn't fixed, you can then try other troubleshooting techniques, such as reinstalling the software.

· If a program is running slowly or otherwise isn't working right, the first thing you should try is closing the program and re-opening it.

· You can also shut down your computer, wait a few seconds, and boot it up again. Some minor problems will work themselves out when you do this.

· Check with the company for any known problems or updates to the software.

· If a program has become completely unresponsive, you can press (and hold) Control+Alt+Delete on your keyboard to open the Task Manager. You can then select the program that isn't working and click End Task. If you are using a Mac, you can press Option+Command+Esc to open a similar dialog box.

     If you get this message when you boot up your computer, it usually means there is a CD, DVD, USB flash drive, or floppy disk in your computer, which is interfering with your computer's booting process. Remove the disk from the drive and restart the computer.

Check for overheating. Make sure the vents in the case are not blocked. Confirm that there is good air flow around the computer.

· Update your antivirus software and scan for viruses.

If you still haven't found a solution to your problem, you may need to ask someone else for help. Try searching the web for the problem that you're having, as other people may have had similar problems. Also, if you have a friend or family member who knows a lot about computers, they may be able to help you.

Keep in mind that most computer problems have simple solutions, although it may take some time to find them. For very difficult problems, a more drastic solution may be required, such as reformatting your hard drive, reinstalling programs, or reinstalling your operating system. If you're not a computer expert, it's possible that you could make the situation worse, so it's best to consult a professional if you think a drastic solution is needed.

If a computer is unable to connect to a network or see other computers on a network, it may be necessary to troubleshoot the network. A network may not work because of any of the reasons below.

1. Network card not properly connected.

2. Bad network card drivers or software settings.

3. Firewall preventing computers from seeing each other.

4. Connection related issues.

5. Bad network hardware.

            Because of the large variety of network configurations, operating systems, setup, etc... Not all of the below information may apply to your network or operating system. If your computer is connected to a company or large network, or you are not the administrator of the network, it is recommended that if you are unable to resolve your issues after following the below recommendations that you contact the network administrator or company representative.

Verify that the network cable is properly connected to the back of the computer. In addition, when checking the connection of the network cable, ensure that the LEDs on the network are properly illuminated. For example, a network card with a solid green LED or light usually indicates that the card is either connected or receiving a signal.

If, however, the card does not have any lights or has orange or red lights, it is possible that either the card is bad, the card is not connected properly, or that the card is not receiving a signal from the network.

If you are on a small or local network and have the capability of checking a hub or switch, verify that the cables are properly connected and that the hub or switch has power.

          Ensure that if this is a new network card being installed into the computer that the card's resources are properly set and not conflicting with any hardware in the computer.

Verify that the network card is capable of detecting or seeing itself by using the ping command. Windows / MS-DOS users ping the computer from a MS-DOS prompt. Unix / Linux variant users ping the computer from the shell.

To ping the card or the local host, type either ping 127.0.0.1 or ping local host This should show a listing of replies from the network card. If you receive an error or if the transmission failed, it is likely that either the network card is not physically installed into the computer correctly, or that the card is bad.

Protocol

Verify that the correct protocols are installed on the computer. Most networks today will utilize TCP/IP, but may also utilize or require IPX/SPX and NetBEUI.

When the TCP/IP protocol is installed, unless a DNS server or other computer assigns the IPX address, the user must specify an IP address as well as a Subnet Mask. To do this, follow the instructions below.

1. Click Start / Settings / Control Panel

2. Double-click the Network icon

3. Within the configuration tab double-click the TCP/IP protocol icon. Note: Do not click on the PPP or Dial-Up adapter, click on the network card adapter.

4. In the TCP/IP properties click the IP address tab

5. Select the option to specify an IP address

6. Enter the IP address and Subnet Mask address, an example of such an

address could be:

IP Address: 102.55.92.1

Subnet Mask: 255.255.255.192

1.       When specifying these values, the computers on the network must all have the same Subnet Mask and have a different IP Address. For example, when using the above values on one computer you would want to use an IP address of 102.55.92.2 on another computer and then specify the same Subnet Mask.

If your computer network utilizes a firewall, ensure that all ports required are open. If possible, close the firewall software program or disconnect the computer from the firewall to ensure it is not causing the problem.

Additional time

In some cases it may take a computer some additional time to detect or see the network. If after booting the computer you are unable to see the network, give the computer 2-3 minutes to detect the network. Windows users may also want to try pressing the F5 (refresh) key when in Network Neighborhood to refresh the network connections and possibly detect the network.

Additional troubleshooting

 If after following or verifying the above recommendations you are still unable to connect or see the network, attempt one or more of the below recommendations.

If you have installed or are using TCP/IP as your protocol you can ping another computer's IP address to verify if the computer is able to send and receive data. To do this, Windows or MS-DOS users must be at a prompt and Linux / Unix variant users must open or be at a shell.

 Once at the prompt assuming, that the address of the computer you wish to ping is 102.55.92.2, you would type:

ping 102.55.92.2

If you receive a response back from this address (and it is a different computer), this demonstrates that the computer is communicating over the network. If you are still unable to connect or see the network, it is possible that other issues may be present.

Another method of determining network issues is to use the tracert command if you are a MS-DOS or Windows user or the trace route command if you are a Linux / Unix variant user. To use this command you must be at the command prompt or shell. Or trace route 102.55.92.2

This should begin listing the hops between the computer and network devices. When the connection fails, determine what device is causing the issue by reviewing the trace route listing.

           Networks are collections of computers, software, and hardware that are all connected to help their users work together. A network connects computers by means of cabling systems, specialized software, and devices that manage data traffic. A network enables users to share files and resources, such as printers, as well as send messages electronically (e-mail) to each other.

           The most common networks are Local Area Networks or LANs for short. A LAN connects computers within a single geographical location, such as one office building, office suite, or home. By contrast, Wide Area Networks (WANs) span different cities or even countries, using phone lines or satellite links.

Plan on the design phase to take anywhere from one to three working days, depending on how much help you have ad how big your network is. Here are the key tasks:

· Settle on a peer-to-peer network or a client/server network.

· Pick you network system software.

· Pick a network language.

· Figure out what hardware you need.

· Decide on what degree of information security you need.

· Choose software and hardware solutions to handle day-to-day management chores. Rolling Out Your Network Rolling out your network requires the following steps:

· Run and test network cables.

· Install the server or servers if you’re setting up a client/server network. (If you are setting up a peer-to-peer network, you typically don’t have to worry about any dedicated servers.)

· Set up the workstation hardware.

· Plug in and cable the Network Interface Cards (NICs – these connect the network to the LAN).

· Install the hub or hubs (if you are using twisted-pair cable).

· Install printers.

· Load up the server software (the NOS, or Network Operating System) if your network is a client/server type.

· Install the workstation software.

· Install modem hardware for remote dial-up (if you want the users to be able to dial into the network).

· Install the programs you want to run (application software).

Configuring Your Network

Network configuration means customizing the network for your own use.

· Creating network accounts for your users (names, passwords, and groups).

· Creating areas on shared disk drives for users to share data files.

· Creating areas on shared disk drives for users to share programs (unless everyone runs programs from their own computer).

· Setting up print queues (the software that lets users share networked printers).

· Installing network support on user workstations, so they can "talk" to your network.

The work you do right after your LAN is up and running and configured can save you huge amounts of time in the coming months.

· Mapping your network for easier management and troubleshooting.

· Setting up appropriate security measures to protect against accidental and intentional harm.

· Tuning up your LAN so that you get the best possible speed from it.

· Creating company standards for adding hardware and software, so you don’t have nagging compatibility problems later.

· Putting backup systems in place so that you have copies of data and programs if your hardware fails.

· Installing some monitoring and diagnostic software so that you can check on your network’s health and get an early warning of impleading problems.

· Figuring out how you plan to handle troubleshooting – educating your LAN administrator, setting up a support contract with a software vendor, and so on.

One key advantage of a peer-to-peer network is that it’s easy to setup. With the simplest sort of peer-to-peer network, you just use the built-in networking that comes with your operating system (Windows 98, Windows XP, Windows 7, Windows 8 and so on) and you have very little software to set up – even less if you have computers that have the operating system preinstalled, as most computers do these days.

For Windows XP and Windows 7, the basic steps to setting up a peer-to-peer network are as follows:

(Review for Cabling) UTP Cable

A UTP cable (category 5) is one of the most popular LAN cables. This cable consists of 4 twisted pairs of metal wires (that means there are 8 wires in the cable). Adding RJ45 connectors at both ends of the UTP cable it becomes a LAN cable they usually use.

You need a UTP Cable, Crimping Tool, RJ45, and Cutter. 

10BaseT and 100BaseT are most common mode of LAN. You can use UTP category-5 cable for both modes. (You can use UTP category-3 cable for 10BaseT, in which there are only 3 wires inside the cable.)

A straight cable is used to connect a computer to a hub. You can use it to connect 2 hubs in the case one of the hubs has an uplink port (and you use normal port on the other hub).

     A cross cable for 10BaseT and 100BaseT is used to connect 2 computers directly (with ONLY the UTP cable). It is also used when you connect 2 hubs with a normal port on both hubs. (In other words, the cross cable is used relatively in a rare case.)