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Chapter 1
Introduction
1.1 Introduction
1.2 About T1 and E1 Trunks
1.3 About AG-T1/E1 and AG Quad Boards
1.3.1 CAS Protocol Call Control Resources
1.4 About Protocol Software
1.4.1 About Trunk Control Programs (TCPs)
1.4.2 About Parameter Files
1.5 Software Requirements
1.5.1 About CT Access
1.5.2 agmon and the AG Configuration File
1.5.3 About The Coprocessor Program (Runfile)
1.5.4 About DSP Program Files
1.6 Creating CAS Protocol Applications
1.1 Introduction
This chapter:
Briefly discusses T1 and E1 trunks.
Explains how AG-T1/ E1 and AG Quad boards are used in computer telephony applications.
Discusses protocol software, and its role in a computer telephony application.
Lists and describes the other software components required in a computer telephony application.
Provides broad outlines for developing computer telephony applications that use digital CAS protocols.
1.2 About T1 and E1 Trunks
A T1
trunk is a type of digital transmission link, used in the United States, Canada, Hong Kong, and Japan. An
E1
trunk is a similar type of link, used mainly in Europe, Asia and South America. T1 trunk lines have a capacity of 1.544 Mbps, and typically handle 24 conversations at once. E1 trunk lines have a capacity of 2.048 Mbps and typically handle 30 conversations at once. (For a detailed description of T1 and E1 communications, see the
AG-T1 and AG-E1 Installation and Developer's Manual
or the
AG Quad Installation and Developer's Manual
.)
1.3 About AG-T1/E1 and AG Quad Boards
NMS AG-T1/E1 and AG Quad boards connect IBM-compatible personal computers to T1 or E1 trunks. AG-T1/E1 boards provide an interface between computers and T1 or E1 trunks and supply 24 or 30 ports of call processing. AG Quad boards provide four T1 or E1 line interfaces for up to 120 ports of call processing, and up to 60 ports of programmable voice processing.
AG-T1/E1 and AG Quad boards connect to other boards over the
MVIP bus
. The MVIP bus is a high-speed, time-division multiplexed digital telephony bus between telephone line interface boards (such as AG and AG Quad boards), that allows boards to share data, signaling, and switching information through a
40-conductor ribbon cable. For example, you can connect multiple AG-T1/E1 or AG Quad boards for applications that perform trunk-to-trunk switching. You can add additional DSP resources, analog line interfaces, or loop start line interfaces, using other AG and Quad boards or board sets. You can also use
MVIP-compatible products from other manufacturers with the AG-T1/E1 or AG Quad boards.
For detailed information on AG Quad boards or CT Access, refer to the
AG Quad Installation and Developer's Manual
or the CT Access Developer's Reference Manual.
WARNING:
Natural MicroSystems obtains board-level approvals certificates for supported countries. Some countries require that you obtain system-level approvals before connecting a system to the public telephone network. To learn what approvals you require, contact the appropriate regulatory authority in the target country.
1.3.1 CAS Protocol Call Control Resources
CAS protocols use DSP resources to setup calls. Although the amount of resources available per board is limited, on AG-T1/E1 boards DSP resources are sufficient to cover 24 (for AG-T1s) or 30 (for AG-E1s) channels at once. However, in some AG Quad board configurations, DSP resources need to be shared among different channels. As a result, trunk control programs (TCP) running on AG Quad boards request DSP resources as needed, and then release these resources when calls are connected. This model of managing resources has some implications concerning the way applications that run on AG Quad boards place and receive calls. These implications are described in
Section 8.4
.
When an application places an outbound call, the TCP requests a call control resource with a timeout. If the timer expires before a call control resource becomes available, the call is aborted and an error is reported to the application. If a call control resource becomes available before the timeout, the TCP performs call setup and notifies the application when the call has reached the connected state.
For inbound calls, as soon as an incoming call is detected, the TCP requests a call control resource with a timeout. The duration of the inbound timeout depends on the telephone protocol the TCP is implementing, and complies with telephone network call setup parameters. If the timeout expires before a call control resource becomes available, the TCP rejects the inbound call and notifies the application of a protocol error. If a resource becomes available before the timeout, the TCP executes the inbound call setup protocol and notifies the application of an inbound call.
1.4 About Protocol Software
To communicate across a T1 or E1 trunk line, parties must signal one another. The scheme used to signal across a telephone line is called a
protocol
. Many different protocol standards are in use throughout the world.
NMS manufactures packages for different protocol families. These families include:
M
ulti-Frequency Compelled protocols based on the R2
standard (
MFC-R2
).
This protocol family includes the CCITT Signaling System R2 (Recommendations Q.400 to Q.490, CCITT Blue Book, 1988) implementation and numerous national variations. These protocols use two-bit line signaling on the signaling channel associated with each voice channel, and in-band MF compelled register signaling.
Pulsed E & M protocols (EAM)
.
This protocol family includes country-specific protocols which use one-bit line signaling, in a pulsed form, and variations on the compelled in-band MF register signaling specified by the CCITT in the 1988 Blue Book. These protocols are specified in different countries by national specifications.
EUropean digital Channel-associated-signaling
(EUC) protocols (EUC) .
This protocol family includes channel associated signaling protocols used in certain European countries. The protocols use two-bit line signaling specified by national standards. The register signaling is either carried by in-band DTMF tones (not compelled) or by out-of-band decadic pulses.
International Wink Start
protocols (IWK).
This protocol family includes country-specific variations of the US Wink Start protocol used in certain countries on T1 trunks. The protocol uses one-bit signaling, and owes its name to the "wink" (short variation in the state of the signaling bit) that the inbound side uses to acknowledge the fact that the outbound side has seized the line. Register signaling is performed by in-band DTMF or MF tones, or by out-of-band decadic pulses.
Signalling System 5
protocol (SS5)
This protocol uses in-band compelled signal frequency tones to perform live signalling and in-band MF tones for register signalling. Since no bits are used, this protocol works the same way on T1 and E1 trunks.
System R1.5
protocols (R15)
This protocol family includes channel associated signaling protocols used for E1 lines in Russia (based on CCITT recommendations Q.511 and Q.544). The protocols use two-bit steady-state line signaling. Register signaling is either carried by in-band MF tones (MF acknowledged pulses) or by out-of-band decadic pulses. Two R15 TCPs are included with the NMS Digital CAS software package. One is used (
r150
) for controlling inbound calls and the other (
r151
) is used for controlling outbound calls.
Most of the protocols in these families have country-specific variations. For this reason, NMS provides parameter files that determine how the protocol works in different countries. The package for each country contains software modules you need to enable AG-T1/E1 or AG Quad boards to communicate with telephone networks in that country.
1.4.1 About Trunk Control Programs (TCPs)
Each protocol software package includes a
trunk control program
(
TCP
), which you load into the on-board memory of an AG-T1/E1 or AG Quad board and configure for a specific protocol. The TCP performs all of the signaling to connect applications with a switch that uses the target country's protocol.
For applications that must support multiple protocols and variations simultaneously, more than one TCP can be loaded to the telephony board. Each line supports one TCP at a time.
The TCPs to be loaded are specified in the AG configuration file (described in
Section 1.5.2,
agmon and the AG Configuration File
). When you run the
agmon
board configuration and monitoring utility (described in
Section 1.5.2
), it downloads the specified TCPs to the board. TCPs run on the AG board processors, so host computers do not have to process the protocols directly.
1.4.2 About Parameter Files
In addition to the basic TCP software, each protocol software package contains binary parameter files
(*.
pf
)
that configure the TCP to work. Each country uses its own protocol implementation, and the parameter file configures the TCP properly for a specific country. CT Access applications loads these parameters automatically at initialization time.
Most of the parameters specified in TCP parameter files cannot be changed. However, you can change a subset of these parameters (specifying digit handling, debugging operation, and miscellaneous options) based on the needs of your application. For more information about loading these parameters, refer to Chapter 5. For information about the parameters for each protocol, refer to
Appendix C
.
1.5 Software Requirements
In addition to the protocol software, you need the following software components to build a CAS protocol application:
CT Access 2.0
or above (if you are using CT Access 2.0, you need Service Pack 2 and AG Access 1.4).
agmon:
An AG board loading and monitoring program.
An
AG configuration file: A
file that specifies how
agmon
configures boards. Sample AG configuration files are supplied with CT Access and with your protocol software (see
Chapter 4
for more information).
Coprocessor software (a
runfile):
The basic on-board processing code, transferred to the AG board by
agmon
(the AG board configuration and monitoring utility). Runfiles are supplied with CT Access.
Several
DSP program files
: Programs that support DSP processing tasks such as DTMF signaling, voice recording and playback. DSP files are supplied with CT Access. Like the runfile, DSP program files are transferred to the AG board by
agmon
.
1.5.1 About CT Access
Applications can control TCPs by using functions from
CT Access
. CT Access is a complete development environment for telephony applications. It provides functions for performing call control, tone and DTMF generation/detection, and voice playing/recording.
CT Access communicates with all TCPs in the same way, making applications protocol-independent. CT Access also includes a Switching service for making and breaking MVIP connections, sending patterns, sampling data, and performing other switching operations according to both the MVIP-95 and MVIP-90 specifications.
Figure 1
shows how the components of a CT Access CAS protocol application relate to one another:
Figure 1. Components of a Typical CT Access CAS Protocol Application
For more information about CT Access, refer to the CT Access documentation.
1.5.2 agmon and the AG Configuration File
When you set up your system, you specify configuration information for all boards in the system in an
AG configuration file
. This information includes:
Whether a board performs MVIP switching
Which board is the MVIP clock master
What software modules to transfer to the board's memory on startup (including which TCPs to load)
Refer to
Chapter 4
for more information about modifying your AG configuration file to set up your protocol software during the board initialization process.
Whenever you make a change to your AG configuration file, launch
agmon
again to make these changes effective. Running the
agmon
utility configures your boards based on the information in the AG configuration file.
agmon
transfers to each board all software modules specified in the file, and performs any other configuration activities needed. It then monitors the boards for errors and other events.
1.5.3 About The Coprocessor Program (Runfile)
The
runfile
is the basic low-level software which an AG board requires to operate. When
agmon
runs, the runfile is transferred from the host into on-board memory, and the board boots. Runfiles have the extension
.run
.
Several runfiles are installed with your CT Access. The AG configuration file specifies which file to use. (For more information about runfiles, see your
AG-T1 and AG-E1 Installation and Developer's Manual
or AG
Quad Installation and Developer's Manual
.)
1.5.4 About DSP Program Files
DSP program files
enable the AG board's on-board digital signal processors to perform certain tasks, such as DTMF signaling, and voice recording and playback. DSP program files are transferred from the host into on-board memory when
agmon
runs.
DSP program files have the extension
.dsp
. Several DSP program files are installed with your CT Access software. Specify the files to use for your configuration in the AG configuration file. (To learn how, see
Chapter 4
.)
Refer to the
AG Runtime Configuration and Developer's Manual
for more information about DSP program files.
1.6 Creating CAS Protocol Applications
Perform the following steps to create a CAS protocol application:
Task
Documentation
Install AG-T1/E1 and/or AG Quad boards in a system.
AG-T1 and AG-E1 Installation and Developer's Manual
AG
Quad Installation and Developer's Manual
Install CT Access.
CT Access Installation Manual
Learn about the parts of the protocol software package.
Chapter 2
of this manual.
Install the protocol software for each country or region that your application will be used in.
Chapter 3
of this manual.
Edit your AG configuration file so it describes all boards in your system.
Chapter 4
of this manual
AG-T1 and AG-E1 Installation and Developer's Manual
AG Quad Installation and Developer's Manual
Test your hardware installation.
AG-T1 and AG-E1 Installation and Developer's Manual
or
AG Quad Installation and Developer's Manual
Configure the call control behavior of your application.
Chapter 6
to
Chapter 8
of this manual.
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Copyright © 1998, Natural MicroSystems, Inc. All rights reserved.
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