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LTX is designed as a turnkey tool for developers of commercial AutoCAD ObjectARX™ add-ons. LTX allows AutoCAD® Runtime Extension (ARX) applications developed for AutoCAD R14 through AutoCAD 2016 to load and run seamlessly in corresponding versions of AutoCAD LT with no recompile required! There are four components provided with LTX:

1. Application setup code which provides a simple GUI for install and uninstall.
2. Runtime code to provide a transparent interface between AutoCAD LT and the application.
3. An SDK and documentation for exposing internal LTX functions to developers.
4. Ongoing technical support and service, including updates and upgrades to LTX code.


LTX supports all variants of AutoCAD LT 97 through AutoCAD LT 2016. The LTX engine supports most ObjectARX™ applications completely and transparently with no code modifications necessary. AutoLISP is not currently supported in LTX.


LTX is licensed as a package including all four components listed above. LTX is licensed separately for each application, where an "application" is a commercial software product that uses one or more ARX libraries to perform a specific function on the user's computer. The license for LTX is provided only for a specified time period (typically 1 year, but may be pro-rated to other time periods on a case-by-case basis), and must be renewed before the time period expires.

Two license fee options are available: a volume based option, and a flat rate option. The volume based option requires an up-front payment of US$1000 per year for the first application and US$500 per year for each additional application, plus US$2 per license sold during the license period, payable at the end of the license period. The flat rate method allows unlimited volume for a flat fee of US$2000 per year for the first application, and US$1000 per year for additional applications, payable at the time the license agreement is executed.

Note that the LTX license is entirely separate from other license agreements which may be in place between the developer and Autodesk, or other companies. It is the developer's responsibility to ensure that use of LTX does not violate other license agreements or contractual obligations to which the developer is bound.


A customized set of files is provided to the developer upon execution of an LTX license agreement. The provided files include the primary LTX module in the form of a Windows DLL file keyed to the licensed application, and the LTX Software Development Kit with additional redistributable LTX implementation files, a fully functional setup utility, and electronic documentation. The application developer ships the LTX redistributable files with the application, along with either the provided setup and uninstall utilities or more specialized setup and uninstall programs which utilize the LTX SDK for installing and removing the application from AutoCAD LT.

Installation of an LTX application involves modifying the user's AutoCAD LT configuration (*.cfg file in AutoCAD LT 97/ 98, system registry in AutoCAD LT 2000 and later) -- no AutoCAD LT files are modified. Specifically, the LTX library is installed as a tee driver which intercepts calls to the first configured output device or display driver in order to perform initialization and loading of the associated application. All calls to the output device are passed directly to the original driver, thus causing the LTX library to be completely transparent to AutoCAD LT.

Once the user installs an LTX enabled application it loads automatically when AutoCAD LT is started. The LTX library creates and maintains a specially modified copy of the original ARX file with an .ltx extension. This modified copy is located in the same folder as the associated ARX file, and is automatically recreated whenever the associated ARX file is updated. Creation of this modified file is nearly instantaneous, so no noticeable delay is seen by the user when this file is initially created.

The application's commands are entered in AutoCAD LT just as they would be in AutoCAD, either by typing them at the 'Command' prompt or by picking the command on a toolbar or menu. The full array of ARX functionality may be utilized by the application, including the use of reactors, custom objects, ADS/RX functions, geometry libraries, etc. The only limitations generally experienced by an LTX application running inside AutoCAD LT are the missing registry based demand-loading feature, the inability to evaluate LISP expressions in any form, and limited ActiveX support.


Are you ready to evaluate LTX with your ARX application? Download our welcome kit to find out how! The LTX Welcome kit includes the license agreement along with instructions and forms for requesting a free LTX evaluation license!

LTX Welcome Kit: (36k)

LTX In Action

Application Manufacturer Description
QuikPik ManuSoft User interface enhancements
Periscope ManuSoft Fast entity feedback
CADLock CADLock, Inc. Drawing file password protection

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