Thursday, 19 September 2019, 03:33 AM

Site: Webmaster Technology Institute
Course: Webmaster Technology Institute (AWS)
Glossary: Global Technical Glossary

C

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Call barring is a mobile phone feature that allows the user to set certain prohibitions on incoming or outgoing calls. This is an effective means to prevent the phone being used to make expensive international or premium rate calls, particularly when the phone is to be used by people other than the subscriber.

Many companies that provide handsets for business use now employ call barring as a security measure, to control their use and restrict calls to pre-approved numbers. The user's personal code must be used to activate this feature.
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Call return is a network service that allows a user to discover the number of the last person who called their phone. The service is activated by dialling a code, e.g. 1471 in the UK or *69 in the USA, and the number then provided will enable the user to return the call.

Call return is part of a general phone feature referred to as Calling Line Identity.

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Call transfer is a mobile phone feature that allows the user to transfer a caller to another phone number. Either party in a phone call can dial a number and then exit from the connection, so leaving the other party ringing the new number.
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Also known as: CW
Call waiting is a phone feature that allows the user to be alerted, while they are engaged in an active call, that another incoming caller is trying to contact them.

Depending on the type of mobile phone, the user might be given an audible 'beeping' warning, or a message on their phone's display screen. This facility gives the user the option of finishing the first call before answering the second one, or alternatively the user could take advantage of call holding to keep the first call 'on hold' while the second caller is dealt with. Other options might be to reject the waiting call, or to send it to the voice mail service.
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Caller group logo is used as a means of identifying either individual callers, or members of specific caller groups.

Caller group logos usually come preloaded with a mobile phone, and are saved by the user under caller groups, or individual callers; they are then displayed whenever that individual user (or a member of the selected group) calls.
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CLIP (Calling Line Identification Presentation) is a supplementary GSM service used to show the number of a caller. When a call is initiated, the caller’s MSC provides the destination MSC with the caller’s identity. The destination MSC then checks to see if the phone being called has subscribed to CLIP. If it has, then the caller’s identity is presented. CLIP couples with CLIR to provide an advanced version of caller line identification in GSM networks.

The presence of CLIP - and CLI generally - can be very useful for choosing to forward or even discard calls from certain people or organisations, as it allows identification of the caller without answering.
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Also known as: CLIR

CLIR (Calling Line Identification Restriction) controls the presentation of caller identity (via CLIP) in GSM networks. If CLIR is enabled, the caller’s MSC indicates this restriction to the destination MSC. The identity is then not forwarded to the destination mobile station.

There is a GSM override function for the CLIR that is available to organisations such as the police, and allows the caller ID to be seen even if they have elected to restrict their identity.
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computer aided manufacturing
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Cameraphone (or Camphone) is the name used to describe a device that combines the features of a mobile phone and a digital camera. This means that a cameraphone not only functions as a normal mobile phone, but it is also capable of taking photographs that can then be transferred over-the-air to other phones. Some cameraphones are even able to record live video clips, and most 3G phones are equipped with a camera enabling them to be used for 2-way video calls.

The usual arrangement is that the camera is completely integrated within the phone body, although there are several models where the camera comes as a plug in accessory. As with other digital cameras, a cameraphone is likely to use either a CCD or CMOS sensor (the two main types), which converts the light entering the lens into an electrical signal, and this signal is processed to produce the photograph. The image may then be viewed on the phone’s screen, or it can be stored in the phone’s internal memory for later use.

Cameraphones typically use small lenses with a fixed focus and aperture, and although these lenses give sharp pictures at a distance of between a few feet and infinity, they are not suitable close-ups (with the exception of a couple of phones that have macro settings). In most cases the lens will be located in a fixed position on the phone, but some have a moveable lens that can be rotated by the user.

Most cameraphones provide limited control over the exposure and other normal camera adjustments, but they do usually offer some means for the user to edit the photographs taken. Many models are fitted with a rather weak LED “flash” light, but a few cameraphones are designed to use a more effective plug in flashgun, which is often available only as an accessory. A digital zoom control is provided to magnify parts of the photograph, although this can worsen the picture quality if over magnified, and due to the way digital zoom operates it is usually unavailable at the higher camera resolutions. Cameraphones are now starting to appear with optical zoom and adjustable lenses, which can only enhance their functionality.

Taking lots of pictures will put a strain on the phone’s internal memory, which is of fixed capacity and shared with other phone features. This problem has been overcome in those phones that have a memory card slot, since a full card can be easily replaced with an empty one, and so an unlimited number of pictures can be stored. As memory cards can be read by other devices, this may prove a convenient way to transfer picture files, or for printing. Phones fitted with Bluetooth™, an infrared port or a data cable connector also offer the user the capability to download their pictures onto other devices, such as their home PC.

Apart from taking photographs of other people or scenes, cameraphones also allow a user to take self-portraits. It is sometimes possible for users to view themselves on the phone’s display screen, if not, most cameraphones have a small mirror fitted near their lens, to help aim the shot. A timer is another universally available feature on cameraphones, which allows a delay to be set for a shot.

The growth of MMS messaging means that many users now exchange photographs between compatible MMS phones, although the size of the MMS file is usually restricted to 100 kB. Some network operators also allow the user to transfer pictures to a Web-based album, so that they can be stored online in a virtual photo album, for sharing with friends and other contacts. Alternatively, the pictures may be sent as attachments to an e-mail address, if the phone has an e-mail facility.

The key feature usually quoted for the quality of a cameraphone is its maximum resolution, a figure given as either a number in pixels (e.g. 1.3 megapixels) or a standard format (e.g. VGA, or 640 x 480 pixels). The resolution determines the best picture quality that the camera can capture, and typically a megapixel camera will be needed to produce acceptable results for standard 6 x 4 inch photographic prints.

The Sharp Corporation launched the J-SH04 - the world’s first camera phone - in Japan in November 2000, and this model included a CMOS image sensor offering a resolution of 110,000 pixels. Today, all the major mobile phone manufacturers produce cameraphones, and the latest models are capable of taking photographs of a similar quality to the average standard digital camera.

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Carrier Signal (Carrier Frequency) is a continuous signal of a single frequency, which is suitable of being modulated with (or carrying) a second information signal.

This is the normal method of transferring information by wireless systems, and in telecommunications the carrier frequency is usually a radio signal of much higher frequency than that contained in the information signal. Optical fibre communication networks use light as a communications medium, and the carrier will then be a laser-generated light beam.
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compact disk
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"(Compact Disc Read-Only Memory). Like music CDs, but may contain information in the form of text, graphics, sound and moving video that can be accessed through a computer. A CD-ROM can store as much information as around 450 floppy discs.",
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compact disk recordable
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compact disk re-writeable
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Real time conversations on the Internet, can occur on the world wide web, Internet relay chat (IRC), through instant messaging, on-line commercial servers (eg AOL or CompuServe). Can be accessed through websites. A chat room is an on-line forum where two or more people can engage in chat (Careaga).
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Checksum is a code used to verify data. It is created by performing a mathematical operation on all the data together, and will change according to the value of the data.

Checksums are used to make transmitted data is correct. When sending data, the transmitter calculates the checksum of the data that is sent, and sends it with the data. The receiver also calculates the checksum of the data it receives. If the checksums don't match then the data�must be�different - i.e. it has not been�correctly transmitted�- and needs to be re-sent.

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cHTML (Compact HTML) is effectively a cut down version of the regular HTML (Hypertext Markup Language) used over the Internet, which has been adapted for use with small computing devices such as personal digital assistants (PDAs), mobile phones, and smartphones. cHTML enables small handheld devices to connect to the World Wide Web, and to present Internet text content on the mobile device's display screen.

Because handheld devices have limitations in their display, power supply, and memory resources, cHTML does not support JPEG images, tables, image maps, multiple fonts, background colours and images, frames, style sheets and more than two colours. As pages are designed to fit the screen, scrolling is also not featured, but four buttons are used to do all the basic operations. However, cHTML does support GIF images.

WML (Wireless Markup Language) is a similar markup language used with the WAP (Wireless Application Protocol). cHTML was originally developed for use with i-Mode devices by Access Company Ltd., a Japanese company, and was accepted by the W3C in 1998.

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Churn is a term referring to customer turnover. The word churn is used to describe those customers abandoning a service or product, and it is particularly applied to Internet and cell-phone subscribers, who tend to often switch providers as a result of intense competition. Churn rate is calculated as the number of customers lost over a time period, divided by the average total number of customers during that period.

For commercial reasons providers will be anxious to understand why the churn rate is high, and whether it is due to customer dissatisfaction with the price or type of services offered. Some providers even offer special deals of free equipment or an initial charge-free period to attract new customers. Also, to discourage churn, the customer may be asked to sign a service agreement containing penalty clauses, to ensure that they stay with the provider for a minimum period
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CIF (Common Intermediate Format) describes a video resolution that is a quarter of the television drawing area. Whilst this should strictly mean 352 x 288 pixels for PAL (used primarily in Europe) and 352 x 240 pixels for NTSC (American) resolutions, the convention of 352 x 288 pixels tends to be globally adhered to by mobile phone manufacturers when describing their screens or cameras.

The acronym CIF was originally brought in to use in the late eighties to early nineties by video conferencing applications but is rarely heard these days as the resolution it describes is relatively small and uncommon, only being used in the context of VideoCD, and more recently mobile phones and low end digital cameras. Common Interchange Format is sometimes also known as D1.

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Circuit switching (Line Switching) is a method of transmitting information (voice, video or other streamed data) between endpoints within telecommunications systems. Each individual subscriber is allocated a dedicated channel of constant bandwidth, which must be maintained open for the duration of their call, even if no actual conversation is taking place and no data being transferred.

Circuit switched systems were used in the old fixed landline telephone networks, for point-to-point connections routed directly between terminals. However, circuit switching may still be the best option when uninterrupted large file transfers need to be sent, or for long voice calls and videoconferencing, but it seems to be mainly suitable for voice traffic. Circuit switching can be considered as the opposite approach to packet switching, which does not require a dedicated channel, and makes more efficient use of the network's resources.