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Appendix A

Glossary


A-law An encoding scheme that determines how an analog speech signal is converted to a digital signal. A-law encoding is used in Europe. The other algorithm, mu-law, is used in North America and Japan. See also mu-law.
AG Natural MicroSystems' Alliance Generation product line of telephony and voice processing hardware and software, including highly integrated hardware modules.
agmon Utility program which reads a configuration file and uses it to load and monitor the AG hardware.
analog Information represented by a continuous and smoothly varying signal amplitude or frequency. Opposite of digital.
API Application Programming Interface; a library of function calls that allow an application developer to access functionality in a uniform and consistent way.
asynchronous Refers to circuitry and operations without a common timing or clock signal.
blocking An API call is blocking if it waits for an internal completion event before proceeding.
channel An electronic communications path for voice data. In digital telephony, a channel usually refers to a separate connection carried on a digital trunk.
circuit switched network A type of wide area network where originating and receiving networks are linked by a single physical circuit, created by a complex switching mechanisms.
compression A procedure for reducing the number of bits needed to convey the information thereby reducing signal bandwidth.
CTA context Organizes services and accompanying resources around a single processing context. Usually represents an application instance controlling a single telephone call. Some contexts are not associated with a call; an application performing voice conversions does not require a telephone line.
ctahd The handle returned by ctaCreateContext.
ctaqueuehd A handle managed by CT Access to access events from one or a group of CTA context handles.
datagram The preferred Internet term for a data packet.
decoding A decompression technique used for changing a digital signal into an analog signal or another type of digital signal.
digital Information in a discrete or quantized form. Opposite of analog.
Digital Signal Processor
See DSP.
DONE event An event sent by CT Access which signifies the completion of an asynchronous function.
DSP Digital Signal Processor; a microprocessor that is designed to perform the calculations required for voice processing.
DTMF Dual-Tone-Multi-Frequency; an in-band signaling system that uses two simultaneous voice-band tones for dialing. Also called touch tone.
echo cancellation An algorithm for analyzing data output on the line so that it can be removed from the received signal.
encoding A compression technique for digitizing and compressing speech data.
event queue The single queue (created by calling ctaCreateQueue) where the application receives all of its events. CT Access provides functions to wait for and retrieve events from the queue. The NMS software is event driven. The events coming from an AG board are placed in an event queue.
Ethernet A local area network hardware, communication, and cabling standard that can link up to 1024 nodes in a network.
events Data structures that contain notification of certain conditions or state changes sent from the hardware or service to the application program. All events are represented as a C data structure. The structure informs the application what event occurred and provides additional information specific to the event. An indication that playing a message is done is a typical event. See also DONE event.
FMIC A Flexible MVIP Interface Circuit (FMIC), which provides a digital time slot switch and MVIP bus interface.
frame (data) The basic data transmission unit used in bit-oriented protocols. A group of data bits arranged in a specific format with a flag at either end to indicate the beginning and end. Because frame format is clearly defined, network equipment can recognize the meaning and purpose of specific bits of data.
full duplex Simultaneous two-way voice and two-way signal data transmission.See also half-duplex and simplex.
gateway application A host with interfaces on more than one network used to route data from one network to another and/or one protocol to another.
G.723.1 A standard algorithm used to compress audio signals. G.723.1 is the approved audio compression standard for H.323. See also H.323.
GSM An algorithm devised by the Global System for Mobile Communications for encoding and compressing PCM data into digital packets.
H.323 A standard of technical requirements for narrowband visual telephone (or audiographics) services. H.323 covers the elements needed for a visual telephone call, including video codecs, audio codecs, shared applications, call control, and system control.
HDLC High Level Data Link Control. A link layer protocol for point-to-point and multi-port communications. In HDLC, control information is placed in a specific position. In addition, the bit patterns used for control information differ substantially from those used for representing data.
IP Internet Protocol. A unique, 32-bit number for a specific TCP/IP host on the Internet, normally printed in decimal form (for example, 128.122.40.227). Part of the TCP/IP family of protocols, it describes software that tracks the Internet address of nodes, routes outgoing messages, and recognizes incoming messages.
IP telephony Internet Protocol Telephony. Technology that lets you make voice phone calls over the Internet or other packet networks using your PC, via gateways and standard telephones.
jitter buffer A mechanism that helps to control the latency of audio/video data on data networks by collecting and rearranging incoming packets to "smooth over" lost or out-of-sequence packets.
ISDN Integrated Services Data Network; a standard for providing voice and data telephone service with all digital transmission and message based signaling.
latency The delay between the time that data is sent from its origin and the time it is received at its destination.
LAN Local Area Network. A network that connects users residing in a relatively close physical proximity to a single physical network.
loopstart The usual method of signaling an off-hook or line seizure, where one end closes the loop and the resulting current flow is detected by the switch at the other end.
MIPS Millions of Instructions Per Second; measure of computer speed according to the average number of machine language instructions performed by the CPU in one second.
mu-law One of two algorithms used in telephony to logarithmically compress or expand digitized speech. mu-law is used in North America and Japan. A-law is the other algorithm used in European networks. See also A-law.
multiplexing The transmission of two or more channels on a single physical circuit.
MVIP Multi-Vendor Integration Protocol; PCM digital bus standard for integrating various board vendors. Facilitates software-controlled digital switching within the PC chassis. MVIP interconnects switching and telephony processing boards on a PC.
MVIP bus A high-speed, multiplexed digital telephony "highway" which allows boards to share data, signaling information, and switching information.
NDIS Network Driver Interface Specification. A device driver specification that provides hardware and protocol independence for network drivers and offers protocol independence so that multiple protocol stacks can coexist in the same host.
nailup To make a permanent assignment, as in nailing up a connection.
network In information technology, a network is a series of points or nodes interconnected by communication paths. Networks can interconnect with other networks and contain subnetworks.
NIC Network Interface Card. An adapter that lets you connect a network cable to a microcomputer. the card includes encoding and decoding circuitry and an input for a network cable connection.
NMS Natural MicroSystems Corporation.
off-hook The active state of a customer telephone circuit. The term is derived from old telephone sets where the receiver, when in use, was lifted from a hook attached to a switch. The opposite condition is on-hook.
packet A unit of data of a fixed size that has been prepared for network transmission.
packet switched network (packet network) A network where no effort is made to establish an electrical circuit between two computing devices. Sending computers divide messages into units called packets, each of which contains the address of the destination computer.
PCM Pulse Code Modulation; a communication technique where the information to be sent is converted into binary numbers which are then transmitted on the signal.
protocol (telephony) Defined procedure for call setup and call teardown.
PSTN Public Switched Telephone Network; a public telephone network.
resources On TX boards, logical entities that define paths or protocol instances between TX Series software entities and peers at other endpoints.
RTP Real Time Transport Protocol. A layer added to the Internet Protocol (IP) that addresses latency problems caused when real-time interactive exchanges (such as video) are conducted over lines designed to carry connectionless data.
RTCP Real Time Transport Control Protocol. A protocol designed to control the latency of audio or videogragraphic data sent over LAN networks.
services In CT Access, a group of logically related telephony functions. A service may be implemented on multiple hardware boards. No matter what hardware is providing the functionality, all services with the same functionality have a standard API. This allows device-independent programming.
stream A grouping of timeslots that usually corresponds to a particular bit-stream of time-domain multiplexed (TDM) serial data on an individual track or wire of a bus.
switch In telephony, a device that can connect one of several inputs to one of several outputs. Switches can range in size from an integrated circuit to an entire build-ing.
switch block The switch on boards that interface the telephone network to the MVIP bus. This switch is normally referred to as the switch block because it may consist of one or more physical switches. It may be either MVIP-compatible or MVIP-compliant.
switch handle Identifies a switching device and allows access to an MVIP switch block.
switching Changing the connections on different boards within a PC platform both during and between phone calls.
synchronous function A function that does not return until its operation is complete.
TCP (internet) Transfer Control Protocol. A transport layer protocol that offers connection oriented, reliable stream service between two hosts.
TCP (telephony) Trunk Control Program; a downloadable module which contains the low-level code to interface with an analog or digital trunk running a certain protocol. TCPs are specific to a trunk protocol, for example, one-way inbound with wink start (which is used for DID and DNIS).
TDM Time Division Multiplexing; a technique for transmitting a number of separate data, voice, and/or video signals simultaneously over one communications medium by quickly interleaving a piece of each signal one after another.
timeslot Specifies a particular 64 kbit/second sub-division of a TDM bus stream. Timeslots number from zero (0) to n where n is stream dependent.
TRAU Transcoding and Rate Adapter Unit. A program or process for converting data streams from one form to another (for example, analog PCM data streams to digital GSM encoded HDLC frames).
UDP User Datagram Protocol. A connectionless, unreliable, transport network protocol for the exchange of replies between network hosts.
virtual port A virtual circuit created on a TX series board in order to connect channels from the PSTN interface to resources at the packet network interface.
vocoder A type of voice coder that converts analog speech into digital signals.
WAN Wide Area Network. A network (such as a PSTN) that connects users and systems across large distances, and usually employs telephone or other long distance media.









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