Telos Zephyr Xstream User Manual page 363

USER'S MANUAL
DS1‐ Digital Signal Level 1 The second level up the digital rate hierarchy used by the Telcos.
This is 24 times the DSØ rate for a total of 1.544 mbps. See DSØ. See also T1.
DS2‐ Digital Signal Level 2 Data rate of 6.312 mbps (4 times the DS1 rate). See DSØ and DS1.
DS3‐ Digital Signal Level 3 Data rate of 43.232 mbps (28 times the DS1 rate). See DSØ and DS1.
DSL‐ Digital Subscriber Line Traditionally refers to an ISDN circuit or sometimes a T1 line,
although the term is also frequently used to mean the next generation beyond ISDN. Sometimes
xDSL is used to indicate that the writer is referring to any of a number of emerging DSL
technologies.
DSU‐ Data Service Unit See CSU/DSU.
DSX‐ 1‐ Digital Cross Connect level 1 (USA & Canada, primarily) Defined as part of the DS1 (T1)
specification and is a closely related signal. The type of signal switched by a Digital Cross‐
Connect System (DACS). The FDL is stripped off at the DACS interface. DSX‐ 1 is also the type of
signal that arrives at the user side of a CSU on a T1 line. A DSX‐ 1 cable is limited to 655 feet (200
meters).
DTE‐ Data Terminal Equipment When using serial communications such RS‐ 232, V.35, or X.21,
the DTE is the device sending/receiving from a modem or CSU/DSU. In contrast to DCE.
DTMF – Dual Tone Multi Frequency The standard tone‐ pairs used on telephone terminals for
dialing using in‐ band signaling. The standards define 16 tone‐ pairs (0‐ 9, #, * and A‐ F) although
most terminals support only 12 of them (0‐ 9, * and #). These are also sometimes referred to as
"Touch Tones". Note that while digital data terminals have the same symbols, ISDN uses
"common channel signaling" (over the D channel) and therefore does not necessarily generate
any tones at all. However many terminals still generate the tones since they will still be used on
occasion to access services (such as voicemail or automated attendant) at the far end using in‐
band tones.
E1 A common type of digital telephone trunk widely deployed outside the US and Canada. Has
31 available 64 kbps channels (called DS 's) plus a sync/control channel for a total data rate of
2.048 mbps.
E‐ 1 See E1
ESF‐ Extended Superframe A type of Line format supported on T1 circuits. The Telco
determines the line format and line encoding of your line. See Line Format.
ETS 300 The pan European ISDN protocol standardized by ETSI. This protocol is used throughout
Europe and has been adopted in many other countries outside the USA & Canada. See also
MSN.
ETSI ‐ European Telecommunications Standards Institute Euro ISDN See ETS 300.
Exchange Another name for a Central Office (most often used in European countries). Also used
in the USA & Canada to refer to a particular 3‐ digit prefix of a 7‐ digit telephone number. See
CO.
Extended Superframe See ESF.
FDL‐ Facilities Data Link A bi‐ directional data link available on T1 circuits when the ESF line
format is used. The FDL is primarily used by the Telco to poll the CSU for error statistics.
Appendix 10 – Glossary 351