Carrier Access SNMP manual Channel Service Unit See DSU/CSU

CHANNEL SERVICE UNIT: See DSU/CSU

CONNECTION: A connection is a logical linkage between timeslots on a span or between spans.

CROSSTALK: Crosstalk occurs when you can hear someone you did not call talking on your telephone line to another person you did not call. You may also only hear half the other conversation (i.e. just one per- son speaking). There are several technical causes for crosstalk relating to cable placement, shielding and transmission techniques.

CUSTOMER PREMISES EQUIPMENT (CPE): Items of telecommunications equipment, such as key systems, PBXs, answering machines, and CSU/DSUs, which reside on the customer’s premises past the net- work interface.

CYCLICAL REDUNDANCY CHECK (CRC): A check sum indicator based on the remainder of a poly- nomial calculation performed on the transmitted data that is used to verify, with some fixed probability of correctness, whether that data was transmitted.

D4 SUPERFRAME (SF) FRAMING FORMAT: The most popular framing format in the T1 environ- ment. Its name stems from the way framing is performed in the D-series of channel banks from AT&T. There are 12 separate 193-bit frames in a superframe. The D4 framing bit is used to identify both the channel and the signaling frame. In D4 framing, signaling for voice channels is carried inband by every channel along with the encoded voice. “Robbed bit signaling” is a technique used in D4 channel banks to convey signaling information. With this technique, the eighth bit (least significant bit) of each of the 24 8-bit timeslots is “robbed” every sixth frame to convey voice related signaling information (on-hook, off-hook, etc.) for each voice channel.

DATA SERVICE UNIT: See DSU/CSU

DATA TERMINAL EQUIPMENT: See DTE

DCE (DATA CIRCUIT-TERMINATING EQUIPMENT):

DIRECT INWARD DIALING (DID): The ability for a caller outside a company to call an internal exten- sion without having to pass through an operator or attendant. In large PBX systems, the dialed digits are passed down the line from the Central Office (CO). The PBX then completes the call.

DIGITAL ACCESS & CROSS-CONNECT SYSTEM (DACS): A digital switch for routing and switch- ing T1 lines (and individual DS0 channels within T1 lines), among multiple T1 ports. It performs all the functions of a normal switch, except connections are typically set up in advance of a call, not together with a call, as in most, low bandwidth voice-band voice and data communications systems. A DACS is basically a manual T1 switch. The Windows-based Remote Monitor software program can be used to implement DS- 0 DACS functionality in the Access Bankô II.

DIP (DUAL INLINE PACKAGE) SWITCH: A tiny switch attached to a printed circuit board with semi- permanent settings that usually requires a ball point pen or small screwdriver to change. There are only two settings - ON or OFF (1 or 0). In the case of the ABII, configurations set by the DIP switches can be mod- ified later through the MS Windows Remote Monitor software installed on a PC.

DIRECT OUTWARD DIALING (DOD): The ability to dial directly from an extension without having to go through an operator or attendant. In PBX and hybrid phone systems, you dial 9, listen to a dial tone, and then dial the outside number you want to reach.