Glossary
CRC (Cyclic Redundancy Check) ◆ A bit errors detection technique that employs an algorithm to calculate a value for the information bits in a packet. The receiver, using the same algorithm, recalculates that value and compares it to the value received. If the two values do not agree, the transmitted packet is considered to be in error.
CS (Controlled Slip) ◆ A CS is the replication or deletion of the pay- load bits of the DS1 frame. A Controlled Slip may be performed when there is a difference between the timing of a synchronous receiving terminal and the received signal.
CSD (Circuit Switched Data) ◆ A
CSU/DSU (Channel Service Unit/ Data Service Unit) ◆ A device which incorporates the functions of a CSU and a DSU and interfaces between a
CSV (Circuit Switched Voice) ◆ A
D channel ◆ One of the three standard channels on a BRI line. At 16 Kbps, a D channel carries all signaling information and can carry low- speed packet data such as X.25 packet switching.
demarc (demarcation point) ◆ The point on a customer’s premises where the line from the telephone company meets the customer’s wiring at the customer’s premises.
Directory Number ◆ Your seven digit telephone number (without the area code), as found in the telephone directory. Each BRI connection can have up to two directory numbers, one for each B channel.
DMA (Direct Memory Access) ◆ A fast method of moving data between two subsystems without processor intervention.
DMS/DMS100 ◆ The name of a central office switch manufactured by Northern Telecom. These switches use Custom (proprietary) or National
DSU ◆ See CSU/DSU.
ETS (European Telecommunications Standard)
ETSI ◆ ETSI is the European Telecommunications Standards Insti- tute.
iSPAN PRI PCI ISDN Users Guide | 135 |