Telos Zephyr Xstream - Manual (Page 360)

USER’S MANUAL
Appendix 10 – Glossary 348
a station contest should not occur as the busy status in response to a call attempt is conveyed
over the separate SS7 network. Therefore, the need for choke exchanges has pretty much
disappeared. Nonetheless, many Telcos still insist that Broadcasters use special choke lines for
call‐ in lines. See blocking and concentration.
Circuit A physical path through which electrical signals can pass. It consists of a network of
conductors and other components, separated by insulators. Technically this term cannot be
applied to fiber optic or other “non‐metallic” paths. See also channel.
Circuit Switched Data See CSD
Circuit Switching A system where a dedicated channel is allocated to the users of that call for
the duration of that call. That channel is allocated for the duration of the call regardless if
information is being transmitted at any given moment. Bandwidth through the channel is fixed,
at no time may this bandwidth be exceeded. If this bandwidth is not used it is wasted. While
inherently inefficient, the dependable and reliable nature of circuit switching makes it ideally
suited to real‐ time voice and audio/video conferencing applications. When over loaded Circuit
Switched networks will respond "all circuits are busy… try again later". This is in stark contrast
packet switched networks or to systems where statistical multiplexing is used. See statistical
multiplexing and Packet Switching.
CLASS‐ Custom Local Area Signaling Services. A variety of enhanced features (usually on analog
lines) that take advantage of the ability of modern SS7 technology’s ability to transmit
information about the calling party. CLASS includes such features as Caller ID, Automatic
Callback, Call Trace (initiated by subscriber), Selective Call Screening, etc.
Clear Cause See Cause Code
CLEC‐ Competitive Local Exchange Carrier Your local telephone service provider who is one of
the new‐ generation providers rather than a RBOC or Independent. A CLEC is really just an
independent, albeit one formed after the divestiture of AT&T. See LEC and Independent.
CLI ‐ Calling Line Identity European term for CLID. See CLID.
CLID‐ Calling Line Identification This is the ISDN and SS7 equivalent of Caller ID; I.E. the number
of the calling party. See also Caller ID and ANI.
CO‐ Central Office The Telco facility to which your local telephone circuit lead. Contains
“Switches” and “Trunks” as well as the local telephone circuits.
Codec‐ COder/DECoder A device which takes digitized audio and “codes” it in order to reduce
the transmission bit rate and which can also simultaneously “decode” such coded audio. Strictly
speaking, a codec does not include an ISDN terminal adapter and related equipment. Simple
codecs are also used in digital telephony. These use a simple companding scheme to reduce
channel noise.
COL ‐ COnnected Line number European Term. The number to which you have connected. This
may not be the number you dialed if call forwarding is used.
Combination Trunk A trunk (channel) which can both make and receive calls. This generally
refers to analog ground start or loop start trunks, although the term can be applied to ISDN BRI
or PRI channels as well. Each combination trunk normally has a telephone number, although
they are frequently part of a hunt group and only one number may be published for that group.