Glossary

 A-LAW: A pulse-code modulation (PCM) algorithm used in digitizing telephone audio signals in E-1 areas.

 ANI: Automatic Number Identification. A feature of certain telecommunications networking protocols or processes that allows the caller's phone number to be detected and displayed by the called party.

 asynchronous function: On Linux platforms, a function that allows program execution to continue without waiting for a task to complete. To implement an asynchronous function, an application defined event handler must be enabled to trap and process the completion event. See synchronous function.

 AT bus: The common communication channel in a PC AT. The channel uses a 16-bit data path architecture. This bus architecture includes the standard PC bus plus a set of 36 lines for additional data transmission, addressing, and interrupt request (IRQ) handling.

 AT-class: Used to describe an IBM or IBM-compatible Personal Computer (PC) containing an 80286 or higher microprocessor, a 16-bit bus architecture, and a compatible BIOS.

 B8ZS: Binary 8-zero Substitution. Basic bipolar coding algorithm for digital telephony. At the transmitting end, a string of 8 zeros is deliberately replaced with a pulse that produces a bipolar violation. At the receiving end, bipolar violations are replaced with a string of 8 zeros.

 BCD: Binary coded decimal. A numbering system often used in data processing where each decimal digit is represented by a four-bit binary value.

 BLT: Board Locator Technology. Operates in conjunction with a rotary switch to determine and set non-conflicting slot and IRQ interrupt-level parameters, thus eliminating the need to set confusing jumpers or DIP switches.

 buffer: A block of memory or temporary storage device that holds data until it can be processed. It is used to compensate for the difference in the rate of the flow of information (or time occurrence of events) when transmitting data from one device to another.

 bus: An electronic path which allows communication between multiple points or devices in a system.

 CAS: Channel Associated Signaling. The signaling protocol used with the CEPT E-1 telephony standard. In CAS, one of the 32 channels, time slot 16, is dedicated to signaling for all of the 30 voice channels. Unlike T-1 systems, which use robbed-bit signaling, telephony systems using CAS are considered examples of out-of-band signaling. See in-band signaling, robbed-bit signaling.

 CEPT: Conference of European Postal and Telecommunications administrations. Defines how bits of a PCM carrier system in E-1 areas will be used and in what sequence. CEPT format consists of 30 voice channels, one signaling channel, and one framing (synchronization) channel. See E-1.

 CCITT: International Telephone and Telegraph Consultative Committee, a part of the ICU (International Telecommunications Union) responsible for formulating telephony and other standards, such as E-1.

 CO: Central Office. The telephone company facility where subscriber lines are linked, through switches, to other subscriber lines (including local and long distance lines).

 CRC: Cyclic Redundancy Check. A basic error checking mechanism for digital transmissions in which a CRC character, indicating the number of bits in a block of data, is included in the transmission. The receiving end calculates the number of bits in the block independently and compares the result to the received CRC character. CRC4 is a specific algorithm used to implement error checking.

 crossover cable: A cable used to interconnect two network boards, often to join two T-1 or E-1 lines. The cable is split and folded so that the lines carrying network receive data on one side of the crossover connector mate with network transmit lines on the other side of the crossover.

 data structure: C programming term for a data element consisting of fields, where each field may have a different type definition and length. The elements of a data structure usually share a common purpose or functionality, rather than being similar in size, type, etc.

 device: A computer peripheral or component that is controlled through a software device driver. A Digital Network Interface board is considered a physical board containing one or more logical board devices, and each time slot on the board is a time slot device.

 device channel: A voice data path that processes one incoming or outgoing call at a time (equivalent to the terminal equipment terminating a phone line). There are 12 device channels on a D/12x. Compare time slot.

 DNIS: Dialed Number Identification Service. An 800 service feature that allows a business to determine the geographical area from which a call originated by the digits dialed (a different phone number is made available to callers in each region).

 drop-and-insert: A system configuration in which two network boards are interconnected by a crossover cable and continuously pass all time slots through to each other. A time slot from one network can be "dropped" to a resource module (such as a D/12x) for processing. In return, the resource module can "insert" signaling and audio into the bit stream received from the other side of the crossover connector. (A resource module can insert only to the network board on the same side of the crossover.) This bit stream is applied through the network module for outbound transmission to the attached network span.

 Digital Network Interface: A general term used to refer to any digital telephony interface board.

 E-1: Another name given to the CEPT digital telephony format devised by the CCITT. See CEPT.

 E&M protocol: A signaling protocol that defines the sending and receiving of signals. E&M protocol is the most common protocol on T-1 trunks.

 8-bit expansion slot: These slots connect additional circuit boards (expansion boards) into the PC bus. The slot contains contacts for the 62 lines of the standard PC bus.

 EPROM: Erasable Programmable Read-Only Memory.

 event: An unsolicited or asynchronous communication from a hardware device to an operating system, application, or driver. Events are generally attention getting messages, allowing a process to decide when and where to redirect its resources.

 event handler: A portion of an application program designed to trap and control processing of device-specific events. The rules for creating a Digital Network Interface event handler are the same as those for creating a Linux signal handler.

 Extended Attribute functions: Class of functions that take one input parameter (a valid device handle) and return device-specific information. For instance, a Digital Network Interface Linux Extended Attribute function returns information specific to the Digital Network Interface class of devices. Extended Attribute function names are case-sensitive and must be in capital letters. See Standard Attribute functions.

 firmware: A set of program instructions that reside (usually in EPROM) on an expansion board.

 in-band signaling: 1. In an analog telephony circuit, in-band refers to signaling that occupies the same transmission path and frequency band used to transmit voice tones. 2. In digital telephony, "in-band" has come to mean signaling that is transmitted within an 8-bit voice sample or time slot, as in T-1 "robbed-bit" signaling.

 IRQ: Interrupt request. A signal sent to the central processing unit (CPU) to temporarily suspend normal processing and transfer control to an interrupt handling routine. Interrupts may be generated by conditions such as completion of an I/O process, detection of hardware failure, power failures, etc.

 Mu-LAW: (1) A pulse code modulation (PCM) algorithm used in digitizing telephone audio signals in T-1 areas.ss (2) The PCM coding and compounding standard used in Japan and North America.

 PC: Personal computer. In this guide, the term refers to an IBM Personal Computer or compatible machine.

 PC AT: An IBM Personal Computer or compatible having the characteristics described under AT-class.

 PC-bus: The common communication channel in a PC. The channel uses an 8-bit data path architecture. The bus contains 62 lines for data and power transmission, addressing, and interrupt request handling.

 peripheral: Any equipment, apart from the central processing unit, that provides a system with outside communication or additional facilities.

 PSTN: Public Switched Telephone Network.

 robbed-bit signaling: The type of signaling protocol implemented in areas using the T-1 telephony standard. In robbed-bit signaling, signaling information is carried in-band, within the 8-bit voice samples. These bits are later stripped away, or "robbed," to produce the signaling information for each of the 24 time slots. See CAS, in-band signaling.

 route: Assign a resource to a time slot.

 16-bit AT expansion slot or 16-bit AT bus slot: These slots connect additional circuit boards (expansion boards) into the bus of AT machines. One of the main features of the AT bus is 16-bit memory data transfer. AT expansion slots are really two slots placed end to end on the motherboard. The larger slot contains contacts for the 62 lines of the standard PC bus. The smaller slot contains contacts for the 36 lines added to the standard PC bus to make up the AT bus.

 SCbus: Signal Computing bus. The TDM (Time Division Multiplexed) resource sharing bus that allows information to be transmitted an received among resources over multiple data lines. A hardwired connection between Switch Handlers (SC2000 chips) on SCbus based products for transmitting information over 1024 time slots to all devices connected to the SCbus.

 SCSA: See Signal Computing System Architecture.

 Signal Computer System Architecture: SCSA. A Dialogic standard open development platform. An open hardware and software standard that incorporates virtually every other standard in PC-based switching. All signaling is out of band. In addition, SCSA offers time slot bundling and allows for scalability.

 signaling insertion: Mode in which the Digital Network Interface (or any network board) overwrites signaling data from resource modules in order to perform signaling to the network (see transparent signaling).

 SRL: Standard Runtime Library. A software resource containing Event Management functions, Standard Attribute functions, and data structures used by all devices, but which return data unique to the device.

 Standard Attribute functions: Class of functions that take one input parameter (a valid device handle) and return generic information about the device. For instance, Standard Attribute functions return IRQ and error information for all device types. Standard Attribute function names are case-sensitive and must be in capital letters. Standard Attribute functions for all devices are contained in the SRL. See Extended Attribute functions.

 synchronous function: On Linux platforms, a function that blocks program execution until a value is returned by the device. Also called a blocking function. See asynchronous function.

 time slot: In a digital telephony environment, a normally continuous and individual communication (for example, someone speaking on a telephone) is (1) digitized, (2) broken up into pieces consisting of a fixed number of bits, (3) combined with pieces of other individual communications in a regularly repeating, timed sequence (multiplexed), and (4) transmitted serially over a single telephone line. Each individual digitized communication is called a time slot. In T-1 areas, 24 time slots are multiplexed onto a single twisted-wire pair. In E-1 areas, 32 time slots are multiplexed together. Compare device channel.

 time slot assignment: The ability to route the digital information contained in a time slot to a specific device channel. See device channel.

 wink: In T-1 or E-1 systems, a signaling bit transition from on to off, or off to on, and back again to the original state. In T-1 systems, the wink signal can be transmitted on either the A or B signaling bit. In E-1 systems, the wink signal can be transmitted on either the A, B, C, or D signaling bit. Using either system, the choice of signaling bit and wink polarity (on-off-on or off-on-off hook) is configurable through Digital Network Interface board download parameters.

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