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Appendix A

Glossary

A-bit One of four bits used to carry channel associated signaling on digital trunks and on MVIP signaling streams. The others are called the B, C and D bits. Many protocols do not use all four bits. Usually, only the A and B bits are used in North America, while all four are used in Europe.
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.
ABCD bits The signaling bits used in channel associated signaling. The value that these bits take determines or indicates the state of the telephone channel. See also CAS.
abort mask A bit mask used with the play and record functions to indicate which DTMF digits abort the respective function. See also DTMF.
addaemon A background process which establishes a system-shared copy of default parameters for AG Access.
address In telephony, the number dialed by a calling party which identifies the party called. Commonly called the phone number.
ADPCM Adaptive Differential Pulse Code Modulation; a method for digitizing and compressing speech data.
ADSI Analog Display Services Interface; a specification for sending display information over ordinary telephone lines. For example, used in caller ID.
AG Natural MicroSystems' Alliance Generation product line of telephony and voice processing hardware and software, including highly integrated hardware modules.
AGC Automatic Gain Control; an algorithm applied to incoming speech before compression and storage so that the amplitude of the stored speech is kept at a target level.
AG driver The hardware device driver that allows AG Access to communicate with all AG boards in a host system.
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.
ANI Automatic Number Identification; a network service that provides a called party with the phone number of the calling party. It 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.
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.
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 Gain Control See AGC.
B bit See A bit.
blind transfer Call transfer method in which AG Access places a second call and then disconnects its port from the PBX before call placement is resolved.
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.
caller ID A telephone company service for delivering the calling party's number between the first and second incoming ring by means of FSK modem signals.
call progress analysis A function that allows the application to control call placement. Call progress monitors in-band energy to detect network tones, voice, and other tones such as modems.
CED CallED party tone; a 2100 Hz burst transmitted by a fax or modem to synchronize the called and calling parties for negotiation.
channel An electronic communications path. In digital telephony, a channel usually refers to a separate connection carried on a digital trunk.
cleardown tone An in-band tone from the CO or switch indicating that the remote party has hung up.
CO Central Office; the place where the public network switch is located.
commands Instructions sent by the application via AG Access to the AG board.
CPE Customer Premise Equipment; customer-owned equipment connected to telephone company lines.
context handle Handle returned from adiOpenPort, which in turn is used for controlling most of the functions in AG Access. Addresses an AG Access port and the associated MVIP timeslot(s). Maps to an AG Access internal context that is referenced whenever a command is issued or an event is received on the port's behalf.
DID Direct Inward Dialing; an incoming telephone service which delivers the final portion of the called address to the CPE, thus allowing the caller to reach an individual extension of a PBX.
DID number Direct Inward Dial number; the called number which is collected by the trunk control program and is passed back to the application.
digital Information in a discrete or quantized form. Opposite of analog.
Digital Signal Processor
See DSP.
DONE event An event sent by AG 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®.
E & M A telephone signaling system used between two switches that uses two wires called the E lead and the M lead. In analog E & M, the M lead of one switch is connected to the E lead of the other, and vice versa. In digital E & M signaling, the A bits and B bits are used.
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 non-existence 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.
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.
FIFO First In, First Out; name given to a queue wherein entries (events, in the AG Access case) are processed in the order they were received.
four-wire In analog telephony, a connection that requires four physical conductors for the voice path, one pair for each direction. If additional wires are required for signaling, they are not counted. In digital telephony, a connection that requires two channels or timeslots, one for each direction. See also two-wire.
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.
frame (speech) The smallest set of samples (sometimes including optional headers or trailers) that a speech compression algorithm requires. Typically, a speech buffer contains multiple frames.
FSK Frequency Shift Keying; a type of analog modem signal that uses two frequencies to send ones and zeroes.
full duplex Simultaneous two-way voice and two-way signal data transmission.See also half-duplex and simplex.
G.726 International Telecommunications Union (ITU) ADPCM standard.
gain (play, record) An amplitude scaling (in dB) applied to played speech after de-compression 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.
Generalized Trunk Protocol (GTP) engine
A framework for controlling the signaling on a telephone line interface with a downloadable module called a Trunk Control Program (TCP).
ground start A method of signaling between two telephony machines where one grounds one side of the line and the other detects the presence of ground.
half-duplex A circuit that can carry information in both directions, but only in one direction at a time. See also full duplex and simplex.
hybrid A circuit that interfaces a bidirectional transmission channel to separate receive and transmit channels.
in-band Audio (voice) path of a telephone line interface.
in-band signaling Signaling where information is carried as audio signals that are transmitted in the voice path. Touch-Tone® dialing is a familiar example. See also out-of-band signaling.
informational event An AG Access event for which there is no internal state change. These events are not automatically generated, but can be made available via the ADICALLCTL eventmask. Does not require any action by the application.
ISDN Integrated Services Data Network; a standard for providing voice and data telephone service with all digital transmission and message based signaling.
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.
inter-pulse delay The time between two active network tone pulses.
line seizure The process by which a switch or station instrument (phone) takes control of a telephone circuit.
local loop The voice-band channel connecting the subscriber to the central office.
loop-start 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.
MF Multi-Frequency; an in-band interoffice signaling method using pairs of frequencies from a set of six available frequencies.
MFC-R2 ITU standard line protocol for E1 lines using compelled MF tones. Note that almost every country has a variant of the standard.
mux handle Operating system-specific object used to wait for an AG Access event to be ready.
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.
nail up To make a permanent assignment, as in nailing up a connection.
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 TCP used when the application does not use AG Access protocol-independent call control. A stateless protocol which does not generate any call control events. This is typically used with low level functions which enable applications to perform call control from the host.
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.
out-of-band Information carried outside of the audio or voice channel.
out-of-band signaling Refers to signaling methods where signaling information is carried by a separate channel. In addition to technical advantages, out-of-band signaling helps prevent unauthorized tampering with the network. See also in-band signaling.
parameters Variables that dictate the behavior of asynchronous functions.
parameter structures Multiple parameters that are grouped together in C language structures.
PBX Private Branch eXchange; a private branch telephone exchange system providing 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.
port The primary object in AG Access on which telephony functions are performed. Physical and logical resources on the AG board are associated with a port.
pulse width The time during which a network tone is active.
protocol (telephony) Defined procedure for call setup and call teardown.
protocol-independent Used to describe AG Access' call control model. All telephony protocols can be represented by this single call control model.
PSTN Public Switched Telephone Network; a public telephone network.
reverse-make-busy A change in out-of-band line signaling to block the remote end from offering any calls.
ring The alerting signal to the subscriber or terminal equipment; also the name for one conductor of a wire pair, designated by R. The other is called tip, or T. See also tip.
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.
simplex A circuit which carries information in only one direction.
SIT Special Information Tone; a series of 3 tones followed by an informational voice message indicating a network error such as congestion or an unknown telephone number.
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.
supervised transfer A call transfer method in which the application controls the transfer process.
SW Utility A utility program for configuring and controlling MVIP boards.
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.
SwitchPath A switching library provided by Natural MicroSystems for MVIP compliant device drivers.
synchronous function A function that does not return until its operation is complete.
task processor A single DSP on an AG board. Each task processor is configured to run one or more DSP programs (downloadable DSP software modules).
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 64kbit/second sub-division of a TDM bus stream. Timeslots number from zero (0) to n where n is stream dependent.
tone cycle The time during which a network tone is active and then absent.
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 AG Access' call control state machine.
trunk A transmission channel connecting two switching machines.
Trunk Control Program (TCP)
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).
two-wire In analog telephony, a connection that requires only two physical conductors. See also four-wire.
WAVE Microsoft file format supporting various speech encodings, typically PCM.
wink An out-of-band signaling method that simulates an off-hook condition for a brief period.
underrun A gap in played or recorded speech caused because the host application did not provide speech buffers to the AG board in a timely fashion; the time limit is a function of the board buffer size and encoding data rate.

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