Hx1-Hx2 Manual-1.4.1 - Telos

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DSLAM – Central Office or wire center based Digital Subscriber Line Access Multiplexer.
What’s on the “other end” of your DSL line. These are sometimes fed by HICAP (High Capacity
or Fiber) facilities to remote wire centers (“remotes” or “vaults”) where “Pair Gain” (carrier)
systems reside, so that DSL service may be provided to customers who otherwise could not be
served due to loop length limitations.
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 inband
tones. The extra 4 tones were originally used in the US military “Autovon” phone network.
E1- A common type of digital telephone trunk widely deployed outside the US and Canada.
Has 31 available 64 kbps channels (called DSØ’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.
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.
Four Wire – A circuit path using separate pairs for send and receive. This term is also used
when referring to digital channels that inherently have discrete send and receive paths, regardless
of the number of pairs (or other media) used. See also Hybrid.
Frame – A unit of data which is defined by the specific communications protocol used. See Line
Format, T1.
FXO – Foreign Exchange Office termination. A line or port meant to connect to the POTS
output of a Central Office. Such an interface goes off and on hook to signal status and expects
to receive ringing current.
FXS – Foreign Exchange Station termination. A line or port meant to connect to a telephone.
Such an interface must look for current flow to know when the attached device goes off-hook.
It must be able to generate ringing current. An FXS port will “run a telephone set”.