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DID (Direct Inward Dial) - A feature offered by key and PBX systems that allows callers to connect directly with PBX users without having to navigate menus or speak with a receptionist.
DIP Switch (Dual In-Line Package Switch) - A small switch usually attached to a circuit board. This switch is used to activate or deactivate the pathways of the circuit board at a specific junction.
DND (Do Not Disturb) - A user-activated function within some telephone systems that makes an extension unavailable to receive internal or external phone calls.
DSL (Digital Subscriber Line) - A network service that provides high-speed data transmission over standard twisted-pair copper wires. DSL service is up to 30 times faster than standard telephone dial-up lines.
DTMF (Dual Tone Multi Frequency) - The frequency tone pairs produced by the dialpad on a touch-tone phone. This signal sends instructions to the switching device to which it is connected. DTMF has all but replaced loop disconnect, or pulse, dialing.
Data compression A technique for storing and transmitting data in a format that requires less space than usual.
Database A collection of organized, retrievable data. The most common types are the relational database and the hypertext database. A relational database stores information in 3 levels: field (any single referenceable item), record (a collection of related fields), and file (a collection of related records). The conventional phone book is an example of a relational database: individual telephone numbers, names and addresses are fields, a line listing is a record, and the complete phone book is a file. Relational databases on computers simplify record retrieval; a user is able to locate a complete record by searching for any of the fields contained in it.

The hypertext database is used mainly on the internet. Hypertext links allow you to point and click on selected words on a web page to link to other locations or pages on the internet. A hypertext database is not organized in any specific relational format.

Dedicated Line A phone line maintained for a specific purpose or function. For instance, a company that performs most of its sales by faxed orders will often have a phone line dedicated to receiving fax transmissions.
Demarcation Point (also Point of Demarcation) - The point at which the line from the phone company’s Central Office (CO) physically passes into a building.
Dial-up A means of establishing an internet connection through the analog Public Switched Telephone Network (PSTN). Dial-up connections require the use of a modem to convert the digital signal from the computer to an analog signal that can be routed by the PSTN.
Dialpad The numbered keys on the telephone. Pressing the number on a dialpad sends instructions to the Central Office (CO) for routing a telephone call.
Digital 1) In telecommunications contexts, digital refers to the method of storing, retrieving, and transmitting data in a sequence of discrete symbols, usually binary. 2) In common usage, digital may refer to a readout that uses numbers rather than scale positions (i.e., digital display, digital clock, etc.).
Digital Adapter A device used to convert a digital phone line to a format compatible with an analog product. Typical uses of a digital adapter include teleconferencing and data transmission through a PBX.
Directory In general, any list that provides access to retrievable contents. On a telephone, a built-in directory is a saved phone list accessible through one or a set of function keys. On a computer, a directory stores retrievable information in an “inverted tree” system. Directories on PCs are also commonly referred to as folders.
Duplex Adapter An accessory that connects to a 1- or 2-line jack that splits the signal and allows more than 1 phone to be connected to the jack. A duplex adapter does not provide an additional connection to the Central Office (CO), but it does permit connection to a second device.
DuraFlex™ The proprietary name for the highly flexible, and durable, headset cords and microphone booms that you'll find on GN Netcom headsets.
dB (Decibel) - 1) A logarithmic expression that provides a relative measure (or ratio) of 2 or more electrical states. The decibel is used to describe differences in signal power and voltage in electronics. 2) An absolute measure for the relative intensity of acoustic sound per unit of area.
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