Computer Network Security

Network security should encompass all aspects of a network from the desktop to the perimeter. A multifaceted and multilayered approach to network security for any organization or business provides the ideal protection coverage against internal and external threats. For small networks or even a single computer, a router with integrated firewall is usually sufficient. For larger networks a dedicated firewall at the network perimeter may be more appropriate. A good number of dedicated firewall appliances can also provide secure Virtual Private Network (VPN) connectivity. The most common feature provided by dedicated firewalls is their ability to inspect, block and report malicious network activity usually initiated from the internet. Firewalls that provide this functionality are often designated as an Intrusion Prevention System (IPS).

A content filtering device is a good complement to a dedicated firewall. These types of devices usually include the ability to monitor, filter, regulate and report on all web related traffic. They are usually installed transparently in line between an internal switch and router or firewall. All internet inbound and outbound traffic is then forced to pass through it. This type of installation is often referred to as "bridged mode." Some content filtering devices can also be integrated with a network directory for individual, detailed monitoring of end user web related traffic. Microsoft Active Directory and Novell eDirectory are examples of directory services that can integrate with a good number of content filtering devices.

Desktops and servers should be protected by antivirus and anti spyware applications. There is a wide variety of enterprise level threat protection software available in today's current marketplace from numerous vendors. The ideal threat protection software should include at a minimum, frequent if not daily virus definition updates, centralized management and reporting, active protection and the ability to guard against unknown threats.

Another aspect of the network that needs security related consideration is what the users are allowed to do on desktops and laptops. Management may want to evaluate and implement access and rights appropriate for their environment and the nature of the organization. Should users be allowed to install software on their own or should the use of removable devices be disabled company wide are examples of issues that should be addressed when defining security policies and procedures.

Lastly, physical security is also important when considering all security related aspects of the network. Servers should be secured and access regulated and documented. It is also best to make sure that backup media is secured whether stored on-site or off-site. In conclusion, a proactive effort in utilizing these network security best practices coupled with consistent monitoring, constant re-assessments and adaptive reconfiguration are all essential in ensuring the safety and protection of an organizations data, intellectual properties and physical assets.

Make Word 2007 Documents

MS Word 2007 is the most preferred text editor among home users and professionals as well. Everyone who uses MS Word 2007 must know how easy it is to create, edit, and format various types of documents in it. However, there is a compatibility issue with Word 2007 i.e. the documents created in it cannot be opened with the MS Word's versions lower than it i.e. Word 97-2003. The file extension in Word 2007 is .docx while in versions from Word 97-2003 documents are saved with .doc extension. Due to the difference in file's extension, Word 97-2003 versions cannot open the document created in Word 2007 and displays compatibility errors. In this article, you know saving Word 2007 document in .doc format.

Saving a Single Document in Word 97-2003 Compatible Format: Execute the following steps to save a Word 2007 document in .doc format:

1. When you are ready to save a document, click the Word 2007 button at top-right corner.

2. Select the Save As option and then Select the Word 97-2003 Document option. The Save As dialog box appears.

3. Select location to save the document.

4. Type a desired name for the document.

5. Click the Save button. The document will be saved at the specified location in .doc format i.e. in Word 97-2003 format.

Configure Word 2007 to Automatically Save All Documents in Word 97-2003 Compatible Format: Apart from saving a single document in .doc format, you can configure Word 2007 to automatically save all documents in .doc format. Configuring Word 2007 is beneficial for those who need to share Word 2007 documents with the users who do not use Word 2007. You can easily configure Word 2007 to automatically save documents in Word 97-2003 compatible format by executing the following steps:

1. Click the Word 2007 button at top-right corner.

2. Click the Word Options button at the bottom. The Word Options dialog box appears.

3. Click the Save option in Left pane.

4. Now, select Word 97-2003 Document (*.doc) in the "Save file in this format" drop-down list in the "Save documents" section.

5. Click the OK button. Word 2007 has been successfully configured.

Now, Word 2007 will automatically save all documents in .doc format. This is how you can make Word 2007 documents compatible with all versions of MS Word.

Atomic Clock

When we consider the most important inventions of the last 100 years, very few people will think of an atomic clock. In fact, if you ask somebody to come up with a top ten of inventions and innovations its doubtful if the atomic clock would figure at all.

Its probably not hard to imagine what people think of as the most life-changing inventions: the Internet, mobile phones, satellite navigation systems, media players etc.

However, nearly all theses technologies rely on accurate and precise time and they would not function without it. The atomic clocks lies at the heart of many of the modern innovations, technologies and applications associated with them.

Let's take the Internet as an example. The Internet is, in its simplest form, a global network of computers, and this network spans time zones and countries. Now consider some of the things we use the Internet for: online auctions, Internet banking or seat reservation for example. These transactions could not be possible with precise and accurate time and synchronisation.

Imagine booking a seat on an airline at 10am and then another customer tries to book the same seat after you on a computer with a slower clock. The computer only has the time to go on so will consider the person who booked after you to have been the first customer because the clock says so! This is the reason any Internet network that requires time sensitive transactions is connected to a NTP server to receive and distribute an atomic clock time signal.

And for other technologies the atomic clock is even more crucial. Satellite navigation (GPS) is a prime example. GPS (Global Positioning System) works by triangulating atomic clock signals from satellites. Because of the high velocity of radio waves an inaccuracy of 1 second could see a sat-nav device out by 100,000 km.

Other technologies too from mobile phone networks to air traffic control systems are completely reliable on atomic clocks demonstrating how underrated this technology is.

Frequency Converters

Recently industry experts have witnessed a surge in the demand for frequency converter or frequency charger. The reason is quite obvious, industries all over the world need energy saving devices in a range of industrial applications and frequency converters are of immense help in resolving the problem to a great extent. The market for frequency converter is expected to enhance by four fold its current size in a couple of years, with reputed suppliers such as Siemens, Groupe Schneider maintaining a major place in the market.

Frequency converter refers to an electronic device that converts AC of one frequency to AC of another frequency. They can also change the voltage, but if it does, that is secondary to its primary purpose. Conventionally a frequency changer is made out of electromechanical components like motor-generator sets or rotary converters. But with the introduction of solid state electronics, you can build totally electronic frequency changers. A frequency converter generally consists of a rectifier stage (producing direct current) which is then reversed to generate AC of the preferred frequency.

If there is a need for voltage conversion, a transformer is generally incorporated in either the ac input or output circuitry and this transformer often gives galvanic isolation between the input and output ac circuits. You can also add a battery to the dc circuitry to improve the converter's ride-through brief outages in the input power. Frequency changers differ in power-handling potential from a few watts to megawatts.

A frequency changer is widely used for export testing, operating equipment manufactured in a foreign country and avionic applications. They are also used in manufacturing industries and research laboratories where higher frequencies are required for special testing.

Voltage Source

A voltage source is generally identified as any device that generates an electromotive force between its terminals or derives a secondary voltage from a principal source of the electromotive force. The major source of voltage can supply energy to a circuit while the secondary voltage disperses energy from a circuit. For instance a common battery is a primary source while a voltage regulator is the secondary source.

A perfect voltage source refers to a circuit element where the voltage across it doesn't have any relation with the current through it. The concept exists only in mathematical models of circuits. If there is any scope of voltage across an ideal source being precised without depending on any variable in a circuit then it is known as an independent voltage source. On the other hand, if the voltage across a perfect source is calculated by some other voltage or current in a circuit, it is called a dependent or controlled voltage source.

A constant voltage source consists of a circuit along with an operational amplifier for supplying an output voltage to a load. In addition there is a feedback circuit for feeding back the output voltage to the equipped amplifier. They also possess a compensation circuit along with a second resistor, a second inductance unit and a second bypass capacitor, one end of each of the second resistor, the second inductance unit and the second bypass capacitor being attached to each other.

The other end of the second resistor is attached to an end of the second inductance unit close to the circuit. While the other end of the second inductance unit is joined to a load side end of the first inductance unit and the other end of the second bypass capacitor is attached to the constant voltage unit.

Current Source

Current source is defined as any electrical device that delivers or absorbs electric current. A current source gives a constant current, as long as the load connected to the source terminals has sufficiently low impedance. A perfect current source is the one that not only restricts the transfer of energy to short circuit and zero voltage but approaches infinite energy and voltage as the load resistance move towards infinity (an open circuit). A perfect current source has endless output impedance in parallel with the source.

As the name suggests constant current source means - the current output will remain constant notwithstanding what the load. But this generally works only for a comparatively narrow range of loads.

Thevenin's Theorem emphasize that regardless of how complex a circuit may appear to be, it can be curtailed to a single source of EMF, such as a single resistance, a single capacitance and/or a single inductor. To be frankly speaking all this is not only true according to the principle, but also works absolutely amazing with some of the very complex circuitry in use nowadays. The idea came into origin and later further developed when circuits were hand built rather that printed on silicon chips.

Nowadays, constant current sources offer a steady output current independent of the load and input power line with variations. Usage of these constant sources consist of producing magnetic fields, evaluating and qualifying products like circuit breakers, relays, transformers, meters, etc.

Mac Or PC?

Which should I buy?

You might have, at least once, stuck between two rallying options. Where? Definitely at a computer shop. Should I get myself a Macintosh(Mac) or a Personal Computer(PC)? Well worry not cause I'm about to clear the air for you.In this post we gonna iron out the differences between the two.

• Software availability:Mac - only general software is easily available; PC - general and custom software both readily available
• Speed:Mac - Low operating speed; PC - Considerably high operating speeds

• Software cost: Mac -dearly priced; PC - fairly priced

• Suitable use: Mac - Any design work (desktop publishing, playing and creating music and videos, slideshows and podcasts); PC - general office work(word documents, keeping records, analyzing data and figures) due to its high speeds
• Design software: Mac - fairly priced; PC - dearly priced
• Ease of software installation: Mac - easy to install and takes less time; PC - installation process is cumbersome and time consuming
• Aesthetic/Look-good value: Mac - considerably edgy and stylish. It never ages cause it always looks cute ; PC - ordinary looking

Food for thought!!!
Three PC engineers and three Mac engineers traveled by train to a conference. At the station, the three PC engineers buy three tickets and watch as the Mac employees buy only a single ticket. " How are three going to travel on only one ticket? asks a PC engineer. "Watch and you'll see," answers the Mac employee.

In the train, the PC engineers take their respective seats, but all three Mac employees cram into a toilet. The conductor comes around collecting tickets. He knocks on the toilet and says,"Ticket, please." The toilet door opens just a crack and a single arm emerges with a ticket in hand. The conductor takes the ticket and moves on. The PC engineers see this and agree it is quite a clever idea.

After the conference, the PC engineers decide to do the same on the return trip and save some money. When they get to the station, they buy a sinlge ticket for the return trip, but the Mac employees don't buy any single ticket.