Telos NX12 user manual Appendix

106   Appendix 2

by the end user. See NCTE and DSX1

CSU/DSU- A device which incorporates the functions of a CSU (Channel Service Unit) and a DSU (Data Service Unit) Most com- monly it interfaces between a Switched-56 or Dedicated Digital Service circuit and a user’s data equipment such as the Zephyr.

CSV- Circuit Switched Voice- A dial-up communications circuit for voice grade communication. Also, the type of ISDN service re- quired to use this capability of an ISDN circuit. In contrast to CSD

Custom ISDN (USA & Canada)- An ISDN protocol which pre-dates National ISDN-1. In most cases National ISDN-1 is also available. The Northern Telecom DMS-100 switch Supports “DMS Custom Functional” ISDN. The AT&T/Lucent 5ESS switch Supports “Custom Point-to-Point” (PTP) and Custom Point-to-MultiPoint (PMP). The ISDN protocol has no relation to where one may call. Telos equipment does not support PMP.

D Channel- Data/Delta Channel. Depending on who you ask, it is Data or Delta. The channel which handles ISDN network-related data between the user’s equipment and the Telco switch. Used to carry data to set up calls and receive calls. Some Telco’s also allow users to use the D channel to access the packet data network, with appropriate terminal equipment.

D4- See Superframe. See also Line Format.

DCE- Data Communication Equipment. When using serial com- munications such RS-232, V.35, or X.21, the DCE is the device sending/receiving from the Telco line. i.e.: a modem or CSU/DSU. In contrast to DTE.

DDS- Digital Data System- See Dedicated Digital Service.

Dedicated Circuit- A permanent channel between two locations. As opposed to a Switched Circuit.

Dedicated Digital Service- a “Hardwired” or “Nailed Up” digital circuit which is permanently connected between 2 points. Typically 56Kbps or 64Kbps. Dedicated digital lines are frequently cheaper than ISDN for full time service. Also called Digital Data System or DDS.

DID- Direct Inward Dialing. The ability for an outside caller to dial to a PBX extension without going through an attendant or auto- attendant. See also DID Number and DID Trunk.

DID Extension or DID station- A specific phone within a PBX which can be called from the public telephone network without going through an attendant or auto-attendant.

DID Number- A phone number used to route calls from the telephone network to a specific phone in a PBX (the DID exten- sion). DID requires special DID trunks or ISDN PRI “two-way DID” trunks. Blocks of DID numbers (typically 10 or 20, some- times higher) are purchased from the LEC or CLEC for use on the PBX. The number of DID numbers usually substantially exceeds the

number of trunks in the system.

DID Trunk- A Direct Inward Dialing Trunk. A trunk (channel) which can only receive calls. A group of telephone numbers (DID numbers) are associated with a given trunk group, however there is no one-to-one correspondence between the individual channels and these numbers. The PBX uses the DID number given it by the phone company to route the channel to the correct DID extension within the PBX. This allows some or all PBX stations to receive calls directly without going through an attendant (or auto atten- dant) Note that there are usually more DID numbers than there are DID trunks. See DID number and DID extension.

Direct Inward Dialing- See DID

Directory Number (USA & Canada)- Your seven digit telephone number (without the area code), as found in the telephone directory.

Directory 1&2 (Zephyr)- The Utility menu on the Zephyr where the 7 digit Directory Numbers can be entered during set up. The Zephyr generally does not require these numbers.

DN- See Directory Number. See also Directory 1 &2 and MSN/ DN 1 &2.

DNIS- Dialed Number Identification Service- A service, typically offered by a long distance company on 800 lines, that provides the number dialed by the caller. This allows a caller to receive specific treatment depending on the number dialed.

DP - Dial Pulse. A method off sending address information by either 1) Causing brief interruptions in loop current. or 2) Caus- ing brief changes of state of a bit on a digital circuit using Channel Associated Signaling. In other words, “rotary” or “pulse” dialing. See also DTMF and CAS.

DSØ- Digital Signal Level Zero. The smallest unit of measure of the standard rate hierarchy used by the Telcos (i.e. all other rates are a multiple of the DSØ rate. For example, the T1 rate is 24 times the DSØ rate and the E1 rate is 32 times the DSØ rate). 64 kbps. See also B channel.

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.