ADTRAN 1200051L5, 61200051L1, 1200051L6, 1200051L2 user manual Dds

Glossary

DDS

dataphone digital service. AT&T private line service for transmitting data over a digital system. The digital transmission system transmits electrical signals direct- ly, instead of translating the signals into tone of varied frequencies as with tradi- tional analog transmission systems. Digital techniques provide more efficient use of transmission facilities, resulting in lower error rates and costs than analog sys- tems.

digital

Referring to communications procedures, techniques, and equipment where infor- mation is encoded as either a binary 1 or 0, the representation of information in dis- crete binary form, discontinuous in time, as opposed to the analog representation of information in variable but continuous waveforms.

DSU

data service unit. A device providing interface between a data terminal or other data communications device and a digital access line.

DTE

data terminal equipment. The portion of a data terminal that interfaces to the end- user’s equipment. The main difference between DCE and DTE is that pins 2 and 3 are reversed on the EIA-232.

Frame

A group of bits sent serially over a communications channel. Generally a local transmission unit sent between data-link-layer entities that contains its own con- trol information for addressing and error checking. The basic data transmission unit is employed with bit-oriented protocols, similar to blocks. In video transmis- sion, a set of electron scan lines that comprise a television picture (usually 525 in the U.S.).

in-band signalling

Signalling made up of tones which pass within the voice frequency band and are carried along the same circuit as the talk path being established by the signals. Vir- tually all signalling (request for service, dialing, disconnect, etc.) in the U.S. is in- band signalling. Most of that signalling is MF (multi-frequency) dialing. The more modern form of signalling is out-of-band.

information element

The name for the data fields within an ISDN Layer 3 message.

interface

A common boundary between two systems over which the inter-system commu- nication occurs.

interworking

Communication between two types of networks or end equipment. This may or may not involve a difference in signalling or protocol elements supported.

61200051L1-1D ISU 2x64 Dual Port ISDN Service Unit User Manual 139