Q: Can I use the 100/200LX as a phone dialer?

A: The HP 95LX had a D/A converter that could drive the speaker and produce touch tones fairly easily; sadly, this feature was dropped in the 100/200LX. That converter is instead used to monitor battery charging.

However, there is a program, called ATDT (ATDT01.ZIP <See Shareware/Freeware index>), which uses some fancy tricks to get touch tones out of a standard PC-AT. It does work on the 100/200LX, and its available on eddie.mit.edu in the hp95lx/ unknown directory. It is not integrated with the Phone Book application, it requires the video mode be set up different from standard (see the README file in ATDT01), and, depending on the phone you use it with, the 100/200LX speaker may not produce sufficient volume to reliably dial.

There is also a program called TT <See Shareware/Freeware index> available, with source code, on eddie.mit.edu. TT comes ready-to-use, but if you have a C compiler and know how to use it, you can modify TT and integrate it into other programs. Like ATDT, TT suffers from the limitations of the volume output from the 100/ 200LX speaker, and your success with it depends on your patience, the sensitivity of your telephones microphone, and the placement of the 100/200LX speaker near the microphone.