* Cinderella the supplier of the Cinderella SDL (support for SDL-92, SDL-96, Z.105, Z.107, and some SDL-2000 features - case sensitivity, data syntax, parameter syntax, textual procedures, range check expression ...), Cinderella MSC and Cinderella SITE (a code-generator that generates ANSI C++ from the Specification and Description Language).
* Dafocus (previously ObjSystem) is the supplier of Encodix (previously EnDec) which can generate matching encoders and coders for G3/UMTS/GPRS etc. and has provided support for the Specification and Description Language.
* IBM Rational
the supplier of the IBM Rational SDL Suite (previously named Tau SDL Suite  and before that SDT) and other related tools. IBM acquired Telelogic, which previously acquired (amongst others):
- CS VERILOG the originator of ObjectGEODE tool for the Specification and Description Language and other related tools.
- Kvatro Telecom (Telelogic Norge AS) that was the supplier of an Specification and Description Language to CHILL translator, integrated with Telelogic's Tau Tool.
* PragmaDev the supplier of PragmaDev Studio which supports the Z.100 series and a variant called SDL-RT for graphical representations of traditional concepts and combines some elements of the Specification and Description Language with other features and C language binding as in SDL-2010. PragmaDev Studio supports testing with the Z.160 series Testing and Test Control Notation, TTCN-3. PragmaDev have produced two videos: Introduction to SDL and Introduction to TTCN.3 .
* SanDri-La  provides a complete Visio add-on application (a Windows DLL by another name) for the creation of Specification and Description Language, MSC URN, TTCN, UML and UML2 diagrams. These diagrams are defined by ITU standards Z.100 series (SDL-2010), Z.109 (UML support), Z.120 (MSC-2000) and Z.160 series (TTCN v3)."
* SAFIRE World for SAFIRE previously marketed by SOLINET, which  a specialist in ready-to-run solutions for signalling systems. SAFIRE (previously SAFIRE-SDL)  is a graphical tool chain designed for the implementation and validation of state machines (FSMs). SAFIRE uses a graphical representation, based on the international standards the Specification and Description Language, MSC, TTCN and ASN.1, in a single environment covering the design, execution and observation of both FSMs and test scenarios. Libraries are offered for standard signalling systems (ISDN, SS7, V5, GSM, INAP, IP, etc) and a corresponding protocol analyzer. 
NOTE: both the SAFIRE World and SOLINET links are to webarchive.org pages.
* SINTEF Telecom and Informatics the supplier of :
    TIMe - The integrated Method - A free 'Electronic Book' (in HTML) for UML, Specification and Description Language and MSC methodology, and previously supplied the flexible Specification and Description Language transformation tool ProgGen ("SDL92" and "SDL88" were supported - probably discontinued contact SINTEF).

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* CATT was the supplier of the Melba tool for the Specification and Description Language
NOTE:Richard Harris wrote on Tuesday, October 23, 2001 4:04 AM:
I regret to inform you that we have effectively closed down the Melba project. I have someone doing a redesign of the Website to close off that area of work.
* Klocwork supplied an MSC to Specification and Description Language synthesizer. Check with Klocwork if this product is still supported as it does not seem to be on their Web site.
* LG Soft Lab (an overseas RD department of LG Electronics Inc.) had a Distributed and Embedded Systems group which supplied
OSD (Object-oriented Software Development).
a Visual Environment for Software Development of real-time distributed systems based on the Specification and Description Language notation also with UML and MSC editors.
However, this work seems to have been discontinued.
* UCS - United Computer Scientists, Ltd ( http://www.ucstec.com/) briefly marketed the ezSDL tool (http://www.ucs.com.pt/ez/Products.htm - dead link) developed by ezLab for Visual Software Development of communication protocols, real-time, event-driven and embedded systems. It was claimed: Specification and Description Language and MSC graphical editors are used for system design; External code may be added; A simulator provided visual debugging; A C code generator targeted: Win32, Linux, VxWorks, QNX. The manual and a demo were available as free downloads. An evaluation version was available. This was announced in November 2004, but by May 2005 the www links had disapperared (but see links above).

Other tool producers, please provide a link to your information.