'D' Glossary Terms

DA - Directory Assistance
Operator-assisted (or virtual operator assisted) telephone directory service which provides the user the phone number and often the address and location of a residence or business. Private or unlisted numbers are not available with this service.

Data Transmission
Data transmission refers to the transfer of data between points in a network.

DCITA - Department of Communications, Information Technology and the Arts
Now referred to as the Department of Broadband, Communications, and the Digital Economy the DBCDE, provides resources for consumers on telephone, Internet, broadband and ICT services and businesses with funding, policy, legislation, reviews, online security and contacts for industry bodies.
See also: ACMA

DDSO - Digital Data Service Obligation
According the ACMA website "The digital data service obligation (DDSO) is the obligation placed on a digital data service provider to ensure that digital data services are accessible to all people in Australia on an equitable basis, wherever they reside or carry on business. The DDSO consists of two obligations - the general DDSO for people in general digital data service areas (approximately 96 per cent of the population) and the special DDSO for people in special digital data service areas (approximately 4 per cent of the population, usually living or working at a distance of more than 4.5 kilometres from their local telephone exchange). Telstra is currently the sole provider of both the GDDS and the SDDS."

Decibel (dB)
The decibel (abbreviated dB) is the unit used to measure the intensity of a sound.
On the decibel scale, the smallest audible sound (near total silence) is 0 dB. A sound 10 times more powerful is 10 dB. Any sound over 85 dB can cause hearing loss.

DECT - Digital Enhanced Cordless Telecommunications
Formerly Digital European Cordless Telephone, DECT is a standard for digital portable or mobile phones, commonly used for domestic or corporate purposes. DECT can also be used for wireless broadband data transfers. DECT is recognised by the ITU as fulfilling the IMT-2000 requirements and thus qualifies as a 3G system.
See also 3G

Desk charger
A mobile phone accessory that enables charging of a mobile handset plus an additional battery in an upright position on a desk.

Desktop Conferencing
Similar to conference calls, a desktop conference between two or more parties is enabled through a desktop computer or laptop and often includes video facilities. The ability to use this feature will depend on bandwidth and hardware configurations.

Dial Tone
This is the tone heard by the user to signal the line is connected and ready for use and is provided by the local switch.

Dial-up
This is an Internet connection that predates broadband and offers much slower Internet access. The customer uses a modem connected to a computer and a telephone line to connect to the Internet Service Provider via the traditional PSTN network.

Dial-up Speed
This is the measure of speed of a dial-up Internet connection and can range from 14kbps to 56kbps.
Related: Broadband

DID - Direct In Dial
A range of 100 defined number variations within a PABX system that allows for the direct dial to a particular handset location rather than using a switch number. A service technician pre-programs the extensions when setting up the PABX.
See also: PABX

Digital
A digital system uses discrete, discontinuous, values to represent information for input, processing, transmission, and storage. In telecommunications this system converts information into binary numeric data, which can be used to represent analogue information. Converting analogue information into digital means that computers and networks can easily interpret the data and it does not deteriorate with reproduction.

Digital Certificates
This is an electronic certificate of authentication used by software programs and Internet sites to verify the identity of users are authors.

Digital Compression
Mathematical technique of compressing a digital signal into a smaller signal, so that it can be transmitted over the same bandwidth at a faster rate.

Digital Signals
The representation, in digital format of analogue signals.

Digital Subscriber Line
A traditional phone line is termed a 'subscriber line'. Assuming that the local exchange is enabled with DSL technology, the use of this subscriber line to deliver digital data at speeds comparable to that of broadband is referred to as a Digital Subscriber Line.
Related: ADSL, SHDSL

Direct-dial call
A non-operator assisted call.

Direct Dialling
Unlike the non-operator assisted call feature, Direct Dialling refers to either Direct In Dial (DID) calls or International Direct Dialling (IDD) calls. IDD (International Direct Dialling) is connection to an international destination without the aid of an operator. IDD is still in use in vernacular because pricing structures quote IDD rates. The second common use for Direct Dialling is for Direct In Dialling whereby a range of 100 defined number variations within a PABX system allows for the direct dial to a particular handset location rather than using a switch number. A service technician pre-programs the extensions when setting up the PABX.
Related: DID, PABX, IDD

Directory Assistance
See DA- Directory Assistance

DoCoMo
DoCoMo is the vendor of the popular overseas phone service i-mode and is a division of Japan's major telecommunications company NTT.

DNS - Domain Name Server
A DNS server acts as a virtual phonebook whereby it translates textual 'human' domain names (www.telstra.com.au) into an Internet Protocol (IP) address - expressed numerically (eg. 100.124.3.1).

Domestic Call
A national call to a number within a country.
Related: STD

Drop Out
See Call Drop Out.

DSL - Digital Subscriber Line
See Digital Subscriber Line.

DSLAM - Digital Subscriber Line Access Multiplexer
Often pronounced Dee-Slam allows telephone lines to make faster connections to the Internet. It is a network device, located in the local exchange, which connects multiple Digital Subscriber Lines to the network.

Dual Band
In mobile telecommunications, Dual Band functionality allows mobile phones to support two frequency bands. This allows for roaming between countries or alternative bands for achieving better coverage in the same country. Common operation frequencies are 900mHz and 1800mHz.
See also Tri-Band, Quad-Band. Not to be confused with a Dual Mode handset.

Dual Mode
In mobile phones Dual Mode refers to the functionality whereby the handset can operate on both the analogue and digital networks regardless of frequency bands.

Duplex
Illustrated by the ability for both parties being able to talk at the same time, Duplex functionality allows for both ends of a communication to send and receive data.