Telecommunications glossary

Telecom glossary - D

DA - Directory Assistance

Phone Number Lookup Service

DAL - Dedicated Access Line

A non-switched circuit from the customer to a carrier.

DDD - Direct Distance Dialing

Any switched telecommunication service (like 1+, 0++, etc.) that allows a call originator to place long distance calls directly to telephones outside the local service area without an operator.

Deactivation

A request to terminate service (or the process of terminating service)

Dedicated Line

A private line leased from a telecommunications carrier.

Default Carrier

Your regular Dial-1 carrier. Call 1-700-555-4141 to find your default carrier.

Dial

To Place A Call On A Switched Network. The term "dial" is obsolete - based on rotary dial phones and electromechanical relay switches (which are nearly non-existent in modern telephone systems.) Touch Tone service recognizes dual tones that are generated as each telephone key is pressed. Where Touch Tone service is not available, telephones and switches electronically "pulse" signals that emulate the older rotary dial telephones. The terms "place" a call or "originate" a call are more accurate than "dial".

Dial Tone

Ready To Place/Originate A Call. When the off hook indication is received at a central office, a dial tone signal is sent to the originating caller on a switched network to indicate that the switch is ready to accept a number.

Dialer

Equipment that pulses out a standard dial protocol signal.

Digital

A device or method that uses discrete variations in voltage, frequency, amplitude, location, etc. to encode, process, or carry binary (zero or one) signals for sound, video, computer data or other information. For example, a digital clock displays the time as discrete numeric values, rather than angular displacement of analog hands. Digital communications technology generally permits higher speeds of transmission with a lower error rate than can be achieved with analog technology. When analog signals are received and amplified at each repeater station, any noise is also amplified. A digital signal, however, is detected and regenerated (not amplified). Unlike amplification, any noise (less than a valid signal) is eliminated by digital regeneration.

Directory Assistance - DA

An information service whereby operators assist customers in obtaining the telephone number(s) they wish to call.