What is an IMEI?

IMEI is an acronym that stands for International Mobile Equipment Identity. Each GSM andUMTS mobile phone has a unique IMEI number. IMEI number facilitates an important function; it easily identifies a mobile phone being used on a GSM (Global System for Mobile Communications) network. The IMEI is a useful tool to stop a phone that is stolen from accessing a network and being used. Mobile phone owners that have their phones stolen can contact their mobile network provider and ask them to ban or shut off a phone using its IMEI number. With an IMEI number, the phone can be banned from the network quickly and easily. It is important to note that swapping a SIM card will not stop a phone from being banned.

An IMEI device is only used to identify the device and does not usually relate to a specific individual or organization. Other numbers such as ESN (Electronic Serial Numbers)and MEID (Mobile Equipment Identifiers) can link an individual to a phone. Usually, an IMSI number stored on a SIM card can identify the subscriber on a network.

There are a few ways in which you can locate your mobile phone's IMEI number, it can usually be found on the handset, beneath the battery, sometimes printed on a small white label. Another way to easily locate your IMEI phone is to dial the following sequence of numbers into the handset: *#06#. If you have a Sony Ericsson mobile phone, you can retrieve the IMEI by pressing the following key sequence: right,*, left, left,*, left, *, left.

The Structure of an IMEI Number

IMEI numbers either come in a 15 digit or 17 digit sequences of numbers. These numbers can identify a handset. Currently the format of the IMEI is AA-BBBBBB-CCCCCC-D.

• These two digits are for the Reporting Body Identifier, indicating the GSMA approved group that allocated the TAC (Type Allocation Code).
• BBBBBB- The Remainder of the TAC
• CCCCCC- Serial Sequence of the Model
• D- Luhn Check Digit of the entire model or 0 (This is an algorithm that validates the ID number)

Central Equipment Identity Register (CEIR)

If a mobile handset is lost or stolen, as the owner or operator of the device, you can contact the CEIR which will blacklist the device in all currently operating switches. This makes the lost or stolen handset unusable. The action of blacklisting stolen mobile handsets is seen as a deterrent to crime, however, it is possible to change an IMEI with special tools and there are certain mobile networks that do not automatically blacklist handsets registered with the CEIR. Current statistics state that about 10% of current IMEI's in use today are not unique or have been reprogrammed (hacked).

CEIR Classification of Handsets

Color	Meaning
White	Valid Mobile Station
Grey	Mobile Station to be tracked
Black	Barred Mobile Station

How CVTs Work

Pulley-based CVTs

Photo courtesy Nissan Global Pulley-based CVT

Peer into a planetary automatic transmission, and you'll see a complex world of gears, brakes, clutches and governing devices. By comparison, a continuously variable transmission is a study in simplicity. Most CVTs only have three basic components:

• A high-power metal or rubber belt
• A variable-input "driving" pulley
• An output "driven" pulley

CVTs also have various microprocessors and sensors, but the three components described above are the key elements that enable the technology to work.

The variable-diameter pulleys are the heart of a CVT. Each pulley is made of two 20-degree cones facing each other. A belt rides in the groove between the two cones. V-belts are preferred if the belt is made of rubber. V-belts get their name from the fact that the belts bear a V-shaped cross section, which increases the frictional grip of the belt.

When the two cones of the pulley are far apart (when the diameter increases), the belt rides lower in the groove, and the radius of the belt loop going around the pulley gets smaller. When the cones are close together (when the diameter decreases), the belt rides higher in the groove, and the radius of the belt loop going around the pulley gets larger. CVTs may use hydraulic pressure, centrifugal force or spring tension to create the force necessary to adjust the pulley halves.

Variable-diameter pulleys must always come in pairs. One of the pulleys, known as the drive pulley (ordriving pulley), is connected to the crankshaft of the engine. The driving pulley is also called the input pulley because it's where the energy from the engine enters the transmission. The second pulley is called the driven pulley because the first pulley is turning it. As an output pulley, the driven pulley transfers energy to the driveshaft.

The distance between the center of the pulleys to where the belt makes contact in the groove is known as the pitch radius. When the pulleys are far apart, the belt rides lower and the pitch radius decreases. When the pulleys are close together, the belt rides higher and the pitch radius increases. The ratio of the pitch radius on the driving pulley to the pitch radius on the driven pulley determines the gear.

When one pulley increases its radius, the other decreases its radius to keep the belt tight. As the two pulleys change their radii relative to one another, they create an infinite number of gear ratios -- from low to high and everything in between. For example, when the pitch radius is small on the driving pulley and large on the driven pulley, then the rotational speed of the driven pulley decreases, resulting in a lower “gear.” When the pitch radius is large on the driving pulley and small on the driven pulley, then the rotational speed of the driven pulley increases, resulting in a higher “gear.” Thus, in theory, a CVT has an infinite number of "gears" that it can run through at any time, at any engine or vehicle speed.

The simplicity and stepless nature of CVTs make them an ideal transmission for a variety of machines and devices, not just cars. CVTs have been used for years in power tools and drill presses. They've also been used in a variety of vehicles, including tractors, snowmobiles and motor scooters. In all of these applications, the transmissions have relied on high-density rubber belts, which can slip and stretch, thereby reducing their efficiency.

The introduction of new materials makes CVTs even more reliable and efficient. One of the most important advances has been the design and development of metal belts to connect the pulleys. These flexible belts are composed of several (typically nine or 12) thin bands of steel that hold together high-strength, bow-tie-shaped pieces of metal.

Metal belt design

Metal belts don't slip and are highly durable, enabling CVTs to handle more engine torque. They are alsoquieter than rubber-belt-driven CVTs.