Appendix G. Glossary
61200305L1-1 ATLAS 550 User Manual G-3
CSU
Channel Service Unit. A device that functions similarly to a modem except that the CSU works with
digital signals rather than analog signaling.
CTS
Clear to send. A signal on the DTE interface indicating that the DCE is clear to send data.
D channel
Delta channel. Controls the operation of the ISDN connection.
DACS
Digital Access Cross-Connect System. An architecture that allows the cross-connecting of several T1
circuits; that is, any DS0 on any T1 circuit can be groomed to any other DS0 on any of the other T1 cir-
cuits in the system.
DCE
Data communications equipment. The part of a computer or data terminal that connects to a commu-
nications channel or network.
dedicated bandwidth
Bandwidth which has been set aside (dedicated) for a specific number.
DHCP
Dynamic Host Configuration Protocol. Allows dynamic IP address allocation.
Dial plan
The numbering plan for ATLAS ports (user and network) handling switched connections. Individual
dial plans contain phone number and features associated with DTMF dialing, PRI and BRI.
DID
Direct Inward Dial. Digits received or transmitted that allow the attached equipment to further route a
call.
Digital Access Cross-Connect System
See DACS.
Discard Eligible (DE)
A flag that can be set to indicate to the network that if excess traffic is received, this frame can be dis-
carded if necessary.
DLCI
Data Link Connection Identifier. Identifies each virtual circuit within a shared physical channel.
DNIS
Dialed Number Identification Service. Service provided by a telephone company that allows the caller
to see what number has been dialed.
DS0
Digital signal (or service) having a transmission rate of 64 kbps intended to carry one voice channel (a
phone call). Also called a fractional T1 because it bridges the gap between 56-kbps direct dial service
(DDS) and a full T1 implementation (24 channels).
