# QSLAC files and trunk control programs

The QSLAC files (quad subscriber line audio - processing circuit) on an AG 2000C board control:

- The 2 wire impedance matching

- Frequency response and equalization

- Trans-hybrid balancing

Each port on the AG 2000C board can be configured separately. The configuration is contained in a QSLAC file. Each QSLAC file is customized for a specific line interface signaling module and for a certain country's two wire return loss requirements.

Refer to Line gain configuration for information on controlling the gain.

## Naming conventions for QSLAC files

All QSLAC files have an extension of .slc and adhere to the following naming convention:

pp cty ss i.slc

Where... | Represents the... | For example...
--- | --- | ---
pp | Two-character NMS product field. | a2 = AG 2000C board
cty | Three-character ISO country code or region code. |
ss | Two-character signaling type. | ls = loopstart
i | One character line impedance field. | 6 = short 600 Ohm lines 9 = short 900 Ohm lines n = lines longer than 2000 feet c = complex (used in some international markets)

For example, a2usals6.slc represents the AG 2000C board/USA/loop start/600 Ohm line QSLAC file.

Natural Access configures the system for the QSLAC file that is intended for your country. Do not change the configuration unless you are confident that a change is required and is allowed by the regulatory agencies.

For more information about QSLAC files, refer to the NMS CAS for Natural Call Control Developer's Manual.

If the default file is not used, an entry is made in the error log file at boot time. If echo cancellation is enabled, there is no benefit in changing from the default QSLAC file.

For example, add the following statement to the board keyword file to load a QSLAC file:

NetworkInterface.Analog[0..23].ConfigFile = a2usals9.slc

## Trunk control programs

Trunk control programs (TCPs) perform all the signaling tasks necessary to interface with the telephony protocol used on the line or trunk. TCPs are loaded onto an AG 2000C board at board initialization. After a TCP has been loaded to the AG 2000C board, the application must start up its protocol before it can use the TCP to perform call control on a specific port.

## QSLAC files and TCPs for loop start

The following table lists the QSLAC files for loop start that can be selected for the United States and Canada:

File | Description
--- | ---
a2usals6.slc | This is the default file that is used when you have a 600 Ohm PBX.
a2usals9.slc | Optimizes performance interfacing to a 900 Ohm PBX.
a2usalsn.slc | Optimizes performance interfacing to long lines (> 2000 feet).

Other QSLAC files are used in other parts of the world. Natural Access configures the correct files for the countries that are supported.

For European countries that are not supported in the installation, use the a2eurlsc.slc file when connecting to the PSTN. Refer to the NetworkInterface.Analog[x].ConfigFile keyword for more information about QSLAC files. Refer to the NMS CAS for Natural Call Control Developer's Manual for information on changing network tone descriptions.

The following table lists the TCPs that are applicable to AG 2000C loop start boards:

Trunk control program | Description
--- | ---
nocc.tcp | No call control.
lps0.tcp | Loop start on AG 2000C.