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Chapter 1

Introduction

1.1 NaturalFax
1.2 CT Access Environment
1.2.1 Programming Model
1.2.2 CT Access Components
1.2.3 Managing NaturalFax Parameters in CT Access

1.1 NaturalFax

NaturalFax is a C function library component of CT Access that provides fax functionality. It runs on the following Alliance Generation (AG) and QX 2000 boards without any additional hardware:

Use NaturalFax to develop an application to transmit and receive Group 3 facsimiles at rates of 14,400 bps and below.

NaturalFax software can be used to produce fax server products for enterprise fax applications, IP telephony gateways, and large scale Fax Service Provider systems. Applications include LAN fax, fax broadcast, fax-on-demand, and store-and-forward and realtime fax over IP data networks.

NaturalFax runs on the Natural MicroSystems hardware which consists of various telecommunications interfaces, a high-speed controller (X86), and an array of DSPs. On the AG boards, the fax modems run on powerful TI C5x and C54x DSPs and share them with other telephony algorithms such as voice record and play. The T.30 fax communication protocol runs on the AG board controller and host processor. This efficient sharing of DSP and controller resources is in contrast to traditional "chip-per-port" designs and provides the highest density and lowest cost/port fax boards and systems.

In the QX family of boards, NaturalFax runs on the TI C549 DSP which serves both as a DSP resource and board controller. The simplified architecture of the four port QX design leads to high performance at a low cost.

NaturalFax supports enhanced Group 3 fax features, such as 1D, 2D, and MMR encoding, Error Correcting Mode (ECM), low, high, and superhigh resolutions, and the standard page width formats. NaturalFax also supports the T.37 format, which is specified as 1D encoding, LOW resolution, and A4 pagewidth. NaturalFax can convert documents into different formats, resolutions, or encodings online (on-the-fly) or offline. NaturalFax supports polling remote fax terminals; a calling fax can poll a remote fax terminal and request the remote terminal to transmit a fax.

For more information about the Group 3 fax standard, see Appendix G.

1.2 CT Access Environment

This section provides background information about CT Access and summarizes the main elements of the CT Access environment. You must have CT Access installed on your system to build applications using NaturalFax.

For more detailed information about CT Access, see the CT Access Developer's Reference Manual.

1.2.1 Programming Model

CT Access employs an asynchronous programming model in order to take advantage of concurrent processing. When called, most functions return immediately, which indicates the operation was initiated. The application may then perform other functions while CT Access is processing the command.

There are two types of functions in CT Access, synchronous and asynchronous.

The following table summarizes the differences between asynchronous and synchronous functions. Chapter 5 lists all NaturalFax functions and indicates if they are synchronous or asynchronous.
Behavior

 Asynchronous

 Synchronous

Operation complete when function returns

 NO

 YES

Returns a DONE event when function is complete

 YES

 NO

Operation can fail after function returns

 YES

 NO

See Appendix C for a complete list of NaturalFax events, and Appendix B for a complete list of NaturalFax errors.

1.2.2 CT Access Components

A CT Access service is a group of logically related telephony functions. The NaturalFax service provides functions to send and receive Group 3 faxes.

A CTA context organizes services and accompanying resources around a single processing context. A CTA context usually represents an application instance controlling a single telephone call. Some CTA contexts are not associated with a call; an operation performing fax file conversions does not require a telephone line.

Note: Only one asynchronous fax operation per CTA context can be active at one time.

A service can only be opened once on an individual CTA context. For example, in order to send faxes using all 24 channels of an AG-T1 board, an application needs to create 24 CTA contexts, and open the NaturalFax service on each CTA context.

An event queue is the communication path from a service to an application. A service generates events indicating certain conditions or state changes. An application retrieves the events from the event queue.

1.2.3 Managing NaturalFax Parameters in CT Access

The characteristics for CT Access services can be altered by modifying associated parameters. Each NaturalFax parameter structure has default values that are sufficient for most configurations. NaturalFax applications typically need to set the Subscriber ID (the telephone number) to comply with FCC or other local regulations, but may not need to modify other parameters.

CT Access manages parameters for services on a CTA context basis. The CTA context maintains a copy of the parameters for all services opened on the context. This allows each fax operation to have its own characteristics.

Use the following CT Access functions to retrieve or modify parameter values:

See Appendix E for detailed descriptions of NaturalFax parameters and their default values.


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