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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.
Add-On A DPNSS supplementary feature which allows a party in an active call to connect a third party in a three-way conference.
address In telephony, the number dialed by a calling party which identifies the party called. Commonly called the phone number.
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.
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.
API Application Programming Interface; a library of function calls that allow an application developer to access functionality in a uniform and consistent way.
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.
B-channel One of the timeslots on an E1 trunk or T1 trunk over which voice data and in-band signaling is passed. B-channel is an abbreviation for bearer channel. See also D channel.
bearer channel See B channel.
bit An acronym for binary digit; the smallest piece of information; a specification of one of two possible alternatives: zero or one.
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.).
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 diversion Diverting a call addressed to one party to another party. In DPNSS, call diversion is implemented as a supplementary feature. Diversion can take place unconditionally (call diversion immediate), or when the wanted party is busy (call diversion busy), or when the wanted party rings but is not answered (call diversion ring no reply).
call hold A DPNSS supplementary feature which allows a party to place the remote party on hold.
call progress 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.
call transfer Causing a call originally connected to one party to be connected to another party. In DPNSS, call transfer is implemented as a supplementary feature.
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.
CEPT E1 A standard used in Europe for digital telephone carriers. CEPT E1 is similar to T1 but operates at 2.048 Mbps and has 32 channels instead of T1's 24. Also referred to as E1.
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.
clear backward To signal that a clear forward signal was received and obeyed.
clear forward To signal a remote party to hang up.
clock A timing reference signal, e.g., on an MVIP bus.
clock master The board that sources the clocks in an MVIP system.
CO Central Office; the place where the public network switch is located.
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.
connection (MVIP) Connects an input terminus to an output terminus. The input and output terminuses can have the same or different buses and streams.
conference In DPNSS, a three-way connection between three parties. Conferences are set up using the DPNSS Add-On supplementary feature.
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.
ctaqueuehd A handle managed by CT Access to access events from one or a group of CTA context handles.
D-channel The timeslot on an E1 trunk or on a T1 trunk in which common channel signaling information is passed. See also B channel and Common Channel Signaling.
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).
digital Information in a discrete or quantized form. Opposite of analog.
Digital Private Network Signaling System
See DPNSS.
Digital Signal Processor
See DSP.
DLL Dynamic Link Library; a library of software object modules that can be loaded and accessed on demand.
DONE event An event which signifies the completion of an asynchronous function.
DPNSS Digital Private Network Signaling System No. 1; a set of codified standards that describe a signaling system for establishing and maintaining simple telephony and data calls. DPNSS is derived from British Telecom's Digital Access Signaling System (DASS).
DSP Digital Signal Processor; a microprocessor that is designed to perform the calculations required for voice processing.
E1 See CEPT E1.
end-to-end layers In the OSI protocol layering model, layers above layer 3 (the network layer). These layers describe how information is exchanged and delivered end-to-end. They also define process-to-process communication, and describe application-independent user services, user interfaces, and applications, etc.
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.
executive intrusion A DPNSS supplementary feature which allows a third party with sufficient clearance to interrupt, or "intrude upon" an active call.
inbound application An application designed to receive inbound calls.
inbound call A call received by an inbound application, placed by a remote party.
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.
International Standards Organization (ISO)
The standards organization that developed the OSI protocol layering model.
intrusion See executive intrusion.
ISDN Integrated Services Data Network; a standard for providing voice and data telephone service with all digital transmission and message based signaling.
ISO See International Standards Organization.
ITU International Telecommunications Union; an international standards body for telecommunications.
layer In the OSI protocol layering model, a level of digital communication. Each layer generally has one or more protocols associated with it.
line A logical telephone connection on which a call can take place.
line arbitration In ME/2/X, automatically choosing from a group of lines the next line for an incoming call or the next line for an outgoing call.
line seizure The process by which a switch or station instrument (phone) takes control of a telephone circuit.
loopback Connecting the inputs and outputs of a device locally. This is typically used for testing purposes.
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.
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.
MVIP connection See connection (MVIP).
network In telephony, short for the telephone switching network.
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.
non-specified information (NSI)
In DPNSS, network-dependent information undefined in the DPNSS specifications. NSI can be sent and received using the DPNSS NSI supplementary feature.
Open Systems Interconnection (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 Interconnection.
outbound application An application designed to place outbound calls.
outbound call A call placed by an application to a remote party.
out-of-band Information carried outside of the audio or voice channel.
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.
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.
port An external connection between the MVIP Bus and anything else, including telephone trunks, human operators, voice processors, FAX processors, etc.
protocol (telephony) Defined procedure for call setup and call teardown.
PSTN Public Switched Telephone Network; a public telephone network.
real channel In DPNSS, a real channel consists of one B channel and its associated signaling. See also virtual channel.
SAP See service access point.
SAPI See service access point identifier.
service access point (SAP)
In the OSI protocol layering model, the point at which a layer provides services to the layer directly above it. With each SAP is associated a unique Service Access Point Identifier (SAPI).
service access point identifier (SAPI)
In the OSI protocol layering model, a unique identifier for a service access point (SAP).
service managers In CT Access, a set of dynamic link libraries (DLL) in Windows NT. You register services in CT Access by calling ctaInitialize with the service and service manager names. Only the services initialized in the call to ctaInitialize may be opened by the application.
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.
SIS See supplementary information strings (SIS)
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.
supplementary features
A range of services (other than basic call control) available in DPNSS, including Call Diversion operations, Call Transfer operations, and others. The range of available supplementary features depends upon the capabilities of the customer's PBX, and upon customer requirements.
supplementary information strings (SIS)
Strings used to send and receive information about DPNSS supplementary features. The strings for each supported DPNSS feature are accessed through SIS identifiers declared in the DPNSS service header file (dpndef.h). Each identifier begins with the prefix DPNSIS_ (for example, DPNSIS_CLC_ORD). The values of SIS identifiers defined in the CT Access DPNSS service are different than the identifier values found in BTNR 188. In your application code, use the DPNSIS_xxx value, and not the SIS identifier code as defined within the BTNR 188 documentation.
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.
Switching service A CT Access service that provides a set of functions for controlling Multi-Vendor Integration Protocol (MVIP) switch blocks on MVIP-compliant switching devices. This service is based on the MVIP-95 device driver standard. It may be used to access MVIP-95 and MVIP-90 device drivers.
synchronous function A function that does not return until its operation is complete.
T1 A standard for telephone transmission that multiplexes 24 digital voice channels on a single 1.544 Mbit/s carrier.
transit working An application performing transit working routes DPNSS messages from one remote party to another remote party without interpreting or acting on these messages.
timeslot Specifies a particular 64 kbit/s sub-division of a TDM bus stream. Timeslots number from zero (0) to n where n is stream dependent.
transitional events A protocol-independent call control event which causes a transition in a state machine.
trunk A transmission channel connecting two switching machines.
trunk signaling See signaling.
virtual call A call made on a DPNSS virtual channel.
virtual channel A logical signaling channel without any associated traffic channel. Virtual channels are used to exchange DPNSS protocol messages without allocating supplementary B channels. See also real channel.

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