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Glossary
•
1TR6: obsolete D-channel switching protocol
used in Germany; replaced by DSS1.
The IBM International ISDN PC Card supports
DSS1, NI-1, and 5ESS, the most widespread D
channel switching protocols. The other protocols
less widely used.
DCE
Data communication equipment
dpi
Dots per inch: a measurement unit for image reso-
lution.
DTE
Data terminal equipment
E carrier
E1 (or E-1) is a European digital transmission for-
system
mat devised by the ITU-TS and given its name by
the Conference of European Postal and Telecom-
munication Administrations (CEPT). It is the Euro-
pean equivalent of the North American T carrier
system format. E2 through E5 are carrier signals in
increasing multiples of the E1 format.
The E1 signal format carries data at a rate of 2,048
Mbit/s and thus can carry 32 channels of 64
kbit/s each. E1 carries at a somewhat higher data
rate than T1 (1.544 Mbit/s) because, unlike T1, it
does not use bit-robbing, so that all eight bits per
channel are used for signal encoding. E1 and T1
can be interconnected for international use.
E2 (or E-2) is a frame that carries four multiplexed
E1 signals at a data rate of 8,448 Mbit/s. E3 car-
ries 16 E1 signals for a data rate of 34,368 Mbit/s.
E4 carries four E3 channels at a data rate of
139,264 Mbit/s. E5 carries four E4 channels at a
data rate of 565,148 Mbit/s.
ETSI
European Telecommunications Standards Insti-
tute.
Euro ISDN
The D-channel switching protocol adopted
throughout Europe. In 1989, 18 telephone compa-
nies from different European states signed a
"Memorandum of Understanding" which led to
the implementation of Euro ISDN in 1993. Euro
ISDN is documented in the ETSI Net-3 standard.
ISDN PC Card – 17 Appendix C: A Brief ISDN Glossary
Appendix C: A Brief ISDN Glossary
201
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