Telos Zephyr Xstream User Manual page 359

USER'S MANUAL
Calling Line ID See CLID. See also Caller ID.
Calling Party Control See CPC.
CAS Channel Associated Signaling. A bit‐ based signaling method used on digital lines (such as
T1) that is periodically inserted into the low order bit also used for the audio transmission. See
Robbed Bit Signaling.
Cause Code A code returned by switching equipment to ISDN equipment as part of the call
control signaling protocol. The cause code indicates that a network call‐ related event has
occurred or has failed. Since these codes actually come from the network, the fact you are
getting a cause code is an indication that that the ISDN circuit is operational at some level.
CCIS Common Channel Interoffice Signaling. A signaling system where network information
such as address and routing information are handled externally to the actual communications
(voice) path. SS7 (Signaling System 7) is the internationally standardized CCIS system.
Deployment of CCIS increased efficiency since no communications (voice) channels are used
merely to report an "all trunks busy" or "far end busy" conditions. It also decreased toll fraud
substantially since it removed the potential for access to the signaling information that was
inherent to in‐ band signaling schemes. CCIS also enables CLASS features as well as sophisticated
re‐ routing features for "intelligent network" applications. See also in‐ band signaling. See also
SS7.
Central Office See CO
Centrex ‐ Central Exchange Service. An enhanced business telephone service intended to offer
most of the features of a PBX but where the lines are all from the LEC out of a public switch.
Offers CLASS‐ like features for business users such as 4‐ digit "inside" dialing, hold, transfer,
attendant, etc.
CEPT‐ Conference on European Posts & Telecommunications. This is a European standards
body that formerly set the standards for telephone interfaces for 26 countries.
CEPT Format The usual rate and frame format for E1 circuits. 2.048 mbps. See E1.
CEPT Rate See CEPT format. See also E1.
Channel An actual path you can talk or send data over. This is what you are paying the phone
company for. For instance, ISDN BRI lines can be ordered with 1 or 2 active channels and these
channels can be configured for voice calls (CSV), data calls (CSD) or both (alternate CSD/CSV). A
channel does not necessarily have it's own unique telephone number. See ISDN.
Channel Associated Signaling See CAS. See also Robbed Bit Signaling.
Choke Exchange A telephone exchange, which is assigned to Radio and TV stations, Promoters,
and other users that will be receiving large numbers of simultaneous calls. The idea is to group
all of these users on a single exchange so when all routes into that exchange are in use "normal"
users (on other exchanges) will not experience blocking of incoming or outgoing calls. Trunks
from other local exchanges into the choke exchange are deliberately limited to just a few paths
so callers will get an "all trunks busy" instead of completely blocking their local exchange.
However, when one of the choke exchange users experiences a large number of calls (as when
your station runs a contest) the other choke exchange users will be blocked because all trunks
into the choke exchange will be busy. In the modern network, using CCIS signaling such as SS7,
actual trunks are not used to convey "busy" or "all trunks busy" conditions. Thus blocking due to
Appendix 10 – Glossary 347