Section 1.9: Principals of Laptops and Portable Devices
The laptop computers or portable computers are quite similar to desktop computers but the same configuration laptop is almost double the cost of the laptop computer. The main advantage of laptop computers is that they are portable. Besides, they use batteries, which make them run for several hours without getting affected by power outage or by short power interruptions. Although they use the components used in desktop computers, they use somewhat different kind of hardware to make them portable. Some of the specific elements used in laptop computers are discussed below.
Section 1.9.1: Docking Station
This is also called a port replicator that contains multiple ports and is mainly used to quickly connect external peripherals to the laptop, as shown in Figure 52. This allows a laptop computer to use external keyboard, full sized monitor, mouse and so on. It allows a laptop computer to use things that it does not have such as a network, a workgroup printer, and so on.
Section 1.9.2: Batteries
Different types of batteries can be used in laptop computers. The batteries that you can use are:
- Nickel cadmium (NiCad): These batteries are not preferable because of there reduced power backup when used with laptops. They need to be recharged after every 3-4 hours. These batteries have a very low energy density compared to the lithium chemistries and NiMH batteries. They also discharge faster than the lithium batteries. To charge and discharge these batteries initially, battery exercising is done so that they may function as expected.
- Nickel metal hydride (NiMH): These batteries are better than NiCad because they can store up to 50% more power and do not used heavy metal with great toxicity as compared to NiCad. NiMH types of batteries do not cause any environmental hazard. The nickel-based batteries, however, are not a best choice for a portable device because the charger applies a full charge each time the portable device is connected to fixed power. Due to this the battery overcharges and elevates temperature that causes permanent capacity loss.
- Lithium-ion batteries (Li-ion batteries): These batteries are lightweight and have a long life. Besides they only receive charge if the charge is low. Because of all these features Li-Ion is the preferred battery chemistry for portable computing devices. However, they are costly as compared to the Nickel batteries. Sometimes you need to calibrate these batteries when they appear as charged while they are not charged. The battery calibration allows you to drain the battery power before recharging it.
To dispose the batteries, you should take them to a recycling center because they should always be recycled. Throwing them and flushing them can contaminate the environment and burning them can explode them.
Section 1.9.3: PCMCIA Cards
The PCMCIA cards are the expansion cards for the notebook PCs. The PC Cards are known for their thinness. They have the same width and length but they vary in thickness. Due to this they are divided into three types: Type 1, Type 2, and Type 3. PCMCIA cards are updated to a new standard called CardBus. This standard has made the devices backward compatible with older PCMCIA slots.
Section 1.9.4: Express Bus
Many laptops now use Mini PCI slot to use wireless adapters. MiniCard is also called Mini PCI (Peripheral Component Interface) Express bus. It is used to implement the PCI Express interface on Notebook computers. Mini PCI is a 32 bit bus that operates at 32MHz and requires only 3.3 volts. It supports three card configurations: Type 1, Type 2, and Type 3. Type 1 and 3 provides support for RJ-45 connector whereas Type 2 cards have RJ-45 connector mounted on them.
Section 1.9.5: Communication Connections
The communication connections common in laptop computers are:
- Bluetooth: This is the short range wireless network namely used in cell phones, handhelds, keyboards and printers. It uses radio waves to exchange data and can operate in the unlicensed industrial, scientific and medical (ISM) band at 2.4 to 2.485 GHz, using a spread spectrum, frequency hopping, full-duplex signal at a nominal rate of 1600 hops/sec. Different Bluetooth specifications for data transmission exist. For example, Version1.2 supports data transmission up to 1 Mbps; Version 2.1+ EDR (Enhanced Data Rate) supports data transmission up to 3Mbps. The three device classes that differ in range and power usage are:
- Class 1 uses 100 milliwatts and can transmit 100 meters.
- Class 2 uses 2.5 milliwatts and can transmit 10 meters
- Class 3 uses 1 milliwatts and can transmit 1 meter
- Infrared: This technology provides wireless connectivity to computing devices to short distances of about 1 KM. It allows you to transfer files and other digital data bi-directionally. However, the signals cannot be encrypted and can only work in the direct line of sight. They cannot penetrate walls or any other kinds of obstructions. This is because they are limited to about one meter and require the devices to be pointed directly at the other devices intended to receive the messages.
- Cellular WAN: This technology provides wireless connectivity over long distances as long as 10 KM using cellular towers, cellular base stations, mobile
telephone switching offices (MTSO), and mobile communication devices. The inclusion of built-in cellular modems is the latest addition to laptop computers. This technology is also referred to as wireless wide area networking or WWAN.
It allows a laptop computer to connect to the Internet through a high-speed cellular phone network when no other access is possible. It can be used on devices such as hand-held phones, notebook computers, pen-based computers, palm-top computers, and portable data collection devices. The cellular technology is flexible enough to take advantage of features and functions of almost any public or private network. The Global System for Mobile Communications (GSM) and Code Division Multiple Access (CDMA) are communication standards for cellular WAN.
- Modem: The modems used in laptops are wireless because laptop is a portable device. A wireless modem connects to a wireless network instead of to the telephone system. It allows you to connect directly to your wireless ISP (Internet Service Provider) so that you can then access the Internet. You can also use your cell phone as a wireless modem, but it offers a very slow speed. For high speed access, you should use broadband wireless modem. Your computer can be attached to a modem using PCMCIA, USB and Serial Port interface. A wireless modem with a USB interface is the best choice.
To protect you computer from wireless networks threats, you can select a modem provide added security features such as 64-/128-bit WEP (Wired Equivalent Privacy) and WPA (Wi-Fi Protected Access). WEP is a system of data encryption used in a wireless network in order to allow authorization control for an 802.11 wireless local area network and WPA is secure 802.11i network standard that ensures the most secure wireless encryption. Wireless devices also use 32-character unique identifier called SSID (service set identifier) that acts as password and is attached to the header of packets that is sent over a wireless local area network (WLAN). All wireless devices on a WLAN must employ the same SSID in order to communicate with each other.
- Ethernet: Ethernet is the wired communication methods of networking that you can use if you want to achieve a high-bandwidth network communications. It uses wires and cables that run from computer to computer. The Ethernet is fast with transfer rates up to 100 Mbps, and is inexpensive to install and maintain. Ethernet has been standardized as IEEE 802.3.
- Wi-Fi: This is a Wireless Ethernet that works on the standard called 802.11b. It works quite similar to regular Ethernet but with no hubs and wires. It allows you to create a wireless connection between devices on network or to the Internet. It is very fast and can operate at up to 11 Mbps speed without any bottlenecks.
There are currently four Wi-Fi standards that can be found on laptop computers. These standards are:
- 802.11b: The oldest standard and most commonly used standard that provides the speed of 11Mbps in the 2.4GHz radio spectrum.
- 802.11g: This standard can provide 54Mbps speeds in the 2.4GHz radio spectrum. It is backward compatible with the 802.11b standard.
- 802.11a: This standard can provide 54Mbps speeds in the 5GHz radio spectrum. It is not backwards compatible due to the different radio frequencies used.
- 802.11n: This is the latest standard. It allows a device to use 2.4GHz or 5GHz radio spectrums and can provide speed up To 270Mbps.
Section 1.9.6: Pointing and Input Devices
A laptop has mouse or a pointing device integrated into it. Beside mouse, a laptop can have pointing devices touchpad, point stick, and trackball. The trackball is a pointing device that consists of a ball held by a socket containing sensors to detect a rotation of the ball. The device also has buttons on the top and a flat, steady surface on the bottom. It is sort of stationary mouse that allows fast scrolling in any direction. Some laptops have one of these devices whereas other may include a combination of these devices.
The input devices in laptops can be stylus that allows you to write directly to the screen.
If a laptop uses a stylus then it would be referred to as a tablet PC.
Section 1.9.7: Power Management
Power management is essential in laptop computers because if a battery gets low without proper warning then your system will be dead and you may loose all data due to sudden shut down. There are a number of power schemes available for laptop computers. The Windows XP allows you to configure power schemes such as:
- Portable/Laptop: This scheme minimizes the use of power when PC is not required. It also adjusts to the processing needs to ensure that the system speed is not sacrificed.
- Max Battery: This scheme minimizes power use but does not adjust according to your processing needs.
Power management can also be done by system states such as hibernate, standby, and suspend options that appear when you shut down your system.