(Page 1 of 1 in this chapter) Version

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.
ADI service Service providing all AG device-level functionality for CT Access. The ADI service is supported by Natural MicroSystems' AG boards. Functions are provided for establishing and maintaining network connections, determining call status, playing and recording voice messages, and generating and detecting DTMF and other tones.
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.
ANI See Automatic Number Identification.
API Application Programming Interface; a library of function calls that allow an application developer to access functionality in a uniform and consistent way.
ASCII American Standard Code for Information Interchange; a standard used for numeric representation of alphanumeric characters.
asynchronous programming
Enables concurrent processing between hardware boards and the host CPU. The application initiates telephony functions on the AG board and continues its own processing instead of waiting for the event from the AG board to arrive. AG Access and CT Access support this model.
Automatic Number Identification (ANI)
A network service that provides a called party with the phone number of the calling party. ANI information is typically available to the called party in R1, R2, and ISDN signaling systems. The implementation of ANI can vary between different telephone companies and even different Central Office switches.
B channel See bearer channel.
basic rate In ISDN, describes a trunk configuration consisting of
2 B channels and one D channel running respectively at 64 kbit/s and 16 kbit/s.
bearer channel (B channel)
One of the timeslots on an E1 trunk or T1 trunk over which voice data and in-band signaling is passed.
blocking An API call is blocking if it waits for an internal completion event before proceeding.
blocking Call control action taken by an application to refuse any further incoming calls. Depending on the protocol, blocking calls will either tell the Central Office or switch not to offer any calls, or to reject every call that is being offered (not answer, or play busy, etc.). See also reverse-make-busy.
blocking system A switching system that does not have enough switching capability to allow all possible sets of connections to be made. Under some circumstances, a connection cannot be made and the call is said to be blocked.
BRI See basic rate.
BRI service Service providing all BX 2000 device-level functionality for CT Access. The BRI service is supported by Natural MicroSystem's BX 2000 boards. Functions are provided for establishing and maintaining network connections and determining call status.
bus In the CT Access Switching service (MVIP-95), specifies the interface point of the switch block. Devices can reside directly on the MVIP bus. Devices can also reside on a board's local bus and may require a switch block to access the MVIP bus.
call control The act of setting up, monitoring, and tearing down a telephone call.
call progress analysis Functions that allow the application to control call placement. Call progress monitors in-band energy to detect network tones, voice, and other tones such as modems.
CAS Channel Associated Signaling; a signaling method where signaling information is provided on a line-by-line or channel-by-channel basis. In-band signaling is a type of Channel-Associated Signaling. See also Common Channel Signaling.
CCITT Comite Consultatif Internationale de Telegraphique et Telephonique
An international organization, based in Geneva, that recommends standard practices for communications. Now publishing under the name of its parent organization - ITU.
CCS See Common Channel Signaling.
Channel Associated Signaling
See CAS.
chained layers In the OSI protocol layering model, the chained layers are the lowest three layers: the physical layer, the data link layer, and the network layer.
channel An electronic communications path. In digital telephony, a channel usually refers to a separate connection carried on a digital trunk. Channel information is carried in timeslots, time-division-multiplexed into a single continuous stream of information.
cleardown tone An in-band tone from the CO or switch indicating that the remote party has hung up.
clock A timing reference signal, e.g., on an MVIP bus.
CO Central Office; the place where the public network switch is located.
codec A device that converts digital signals to analog, and vice versa.
Common Channel Signaling
A signaling method where signaling information is provided for a number of channels in data-packet form sent over a separate link. This separate link is usually another channel of the same digital trunk, called a D channel in ISDN service.
completion event The last event to be generated in response to a command. See DONE event.
CT Access Natural MicroSystems' development environment for telephony applications.
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.
D channel The timeslot on an E1 trunk or on a T1 trunk in which common channel signaling information is passed.
data link layer In the OSI protocol layering model, the data link layer (layer 2) is the layer above the physical layer. Protocols for this layer describe methods for error-free communication between devices across the physical link. One protocol used at this layer is CCITT recommendation Q.921, also known as Link Access Procedures on the D Channel (LAPD).
dB See decibel.
dBm A unit of measure of absolute power level, defined as the number of decibels above or below a level of one milliwatt.
decibel (dB) A unit of measure of relative power or voltage in terms of the ratio of two values. dB = 10 log (P1/P2), where P1 and P2 are the power level in watts.
default channel The B channel assigned to a CTA context when it is created.
DONE event An event 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.
echo cancellation An algorithm for analyzing data output on the line so that it can be removed from the received signal.
encoding (speech) Any of the compression techniques for digitizing and compressing speech data.
energy detector An algorithm for reporting the existence and nonexistence of signals and audio on a telephone line based on a set of qualifying parameters. Examines the in-band signal to distinguish between silence and energy.
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.
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.
exclusive mode One of two modes which determine what the BRI service does if the network denies the service use of its default channel. In exclusive mode, the BRI service aborts the call.
FSK Frequency Shift Keying; a type of analog modem signal that uses two frequencies to send ones and zeroes.
G.726 International Telecommunications Union (ITU) ADPCM standard.
gain (play, record) An amplitude scaling (in dB) applied to played speech after decompression or to recorded speech prior to compression.
glare The simultaneous occurrence of an attempt to place a call and the appearance of an incoming call on the same line. In general, the incoming call must be given precedence.
Hertz (Hz) The unit of frequency. One hertz equals one cycle per second.
hybrid A circuit that interfaces a bidirectional transmission channel to separate receive and transmit channels.
Hz See Hertz.
H.100 bus A PCM digital bus standard for integrating various board vendors. Allows boards to share data, signaling, and switching information.
in-band Audio (voice) path of a telephone line interface.
inbound application An application designed to receive inbound calls.
informational event An event for which there is no internal state change; these events are not automatically generated, but can be made available via an eventmask parameter. Does not require any action by the application.
Integrated Services Digital Network (ISDN)
A standard for providing voice and data telephone service with all digital transmission and message-based signaling.
International Standards Organization (ISO)
The standards organization that developed the OSI protocol layering model.
inter-pulse delay The time between two active network pulse tones.
ISO See International Standards Organization.
ITU See CCITT.
IVR Interactive Voice Response; a telephony application in which callers interact with a program using voice prompts, DTMF digits, speech recognition, etc., for querying or delivering information.
LAPD See Link Access Procedures on the D Channel.
LAPD stack mode An AG ISDN protocol stack mode in which the stack implements layer 2 functionality only. No channelizer or ACU is present. The application communicates directly with the data link layer.
layer In the OSI protocol layering model, a level of digital communication. Each layer generally has one or more protocols associated with it.
LE An ISDN equipment category. LE is Local Exchange equipment.
line A logical telephone connection on which a call can take place.
Link Access Procedures on the D Channel (LAPD)
CCITT recommendation Q.921: a protocol for communication at the data link layer.
local loop The voice-band channel connecting the subscriber to the central office (CO).
loop start A method of signaling an off-hook or line seizure, where one end closes the loop circuit and the resulting current flow is detected by the switch at the other end.
MF Multi-Frequency; an in-band interoffice tone-based signaling method using pairs of frequencies from a set of six available frequencies.
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.
muxhandle Operating system-specific object used to wait for an event to be ready.
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.
network layer In the OSI protocol layering model, the network layer (layer 3) is the layer above the data link layer. Protocols for this layer describe methods for transferring information between computers. They also describe how data is routed within and between networks. One protocol used at this layer is CCITT recommendation Q.931.
NMS Natural MicroSystems Corporation.
NMS ADPCM A form of ADPCM that requires less processing power than the CCITT standard.
NOCC (Null Protocol) NO Call-Control; the trunk control program used when the application does not want to use protocol-independent call control. NOCC is a stateless protocol which does not generate any call control events. It is typically used with low level functions which enable applications to perform call control from the host.
Non-Exclusive Mode (Also called Preferred Mode) One of two modes which determine what the BRI service does if the network denies the service use of its default channel. In Non-Exclusive Mode, the BRI service will accept any B channel that the network assigns.
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.
OGT Out-Going Trunk; a telephone line that is used only for placing calls.
OKI ADPCM A form of ADPCM used on some voice boards.
Open System Interconnect (OSI)
A model for digital communication, developed by the International Organization for Standardization (ISO). In OSI, seven separate layers of communication are defined.
OSI See Open Systems Interconnect (OSI).
out-of-band Information carried outside of the audio or voice channel.
outbound application An application designed to place outbound calls.
outbound call A call placed by an application to a remote party.
parameters Variables that dictate the behavior of functions.
parameter structures Multiple parameters that are grouped together in C language structures.
PBX or PABX Private (Automatic) Branch Telephone eXchange; a system providing local telephone switching in an office or building.
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.
pending command A command that has been sent, but has not yet been acknowledged with its associated event.
physical layer In the OSI protocol layering model, the physical layer (layer 1) is the electrical and mechanical layer. Protocols for this layer describe, on an electrical and mechanical basis, the methods used to transfer bits from one device to another. One protocol used at this layer is CCITT recommendation I.430/I.
PRI See primary rate.
primary rate In ISDN parlance, a term used to describe a trunk configuration consisting of 23 B channels and one D channel running at 1.544 Mbit/s (or 30 B channels and 1 D channel at 2.048 Mbit/s in Europe).
Preferred Mode See Non-Exclusive Mode.
protocol (telephony) Defined procedure for call setup and call teardown.
protocol-independent Used to describe call control model. All telephony protocols can be represented by this single call control model.
PSTN Public Switched Telephone Network; a public telephone network.
Pulse Code Modulation
See PCM.
pulse width The time during which a network tone is active.
Q.921 See Link Access Procedures on the D Channel.
Q.931 CCITT recommendation Q.931 describes a protocol for the network layer (layer 3 in the OSI protocol layering model).
reverse-make-busy A change in out-of-band line signaling to block the remote end from offering any calls.
S-bus A CCITT I.430 BRI configuration.
service managers Dynamic link libraries (DLL) in Windows NT and shared libraries in UNIX which are linked to the application. Service managers implement services, execute within the CT Access environment, and adhere to standard CT Access interfaces.
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.
signaling The transmission of information about a line's on-hook or
off-hook status and various related signals including those that deliver address information.
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.
SUCCESS A return code that for asynchronous functions signifies the function was initiated. For synchronous functions, SUCCESS means that the function was completed. Note that for functions that require board resources, SUCCESS means that the commands necessary to execute the function on the board were delivered to the board. An error can still be returned in an event later.
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.
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.
time division multiplexing
See TDM.
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.
tone detector Employs a precise tone filter to detect single or dual frequency tones.
transitional events A protocol-independent call control event which causes a transition in a state machine.
trunk A transmission channel connecting two switching machines.
underrun A gap in played or recorded speech caused because the host application did not provide speech buffers to the board in a timely fashion. The time limit is a function of the board buffer size and encoding data rate.
wait object Operating system dependent objects that signal requests for services when waited upon in an OS dependent manner. These objects are managed by the dispatcher on specific ctaqueuehds.

(Page 1 of 1 in this chapter) Version

tech_support@nmss.com