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
Frame
A group of bits sent serially over a communications channel. Generally a local transmission unit sent between
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
information element
The name for the data fields within an ISDN Layer 3 message.
interface
A common boundary between two systems over which the
interworking
Communication between two types of networks or end equipment. This may or may not involve a difference in signalling or protocol elements supported.
ISU 2x64 Dual Port ISDN Service Unit User Manual | 139 |
