The 22.214.171.1241 version of CallTTY is provided as a free download on our software library. CallTTY lies within Communication Tools, more precisely Instant messaging. The current installation package available for download requires 880 KB of hard disk space. The most popular version of the CallTTY is 2.3. The actual developer of the software is DXsoft group. Commonly, this program's installer has the following filename: CALLTTY.EXE. Our antivirus analysis shows that this download is malware free.
From the developer:
A program to communicate with phone TTY/TDD devices (Telecommunications Devices for the Deaf) via a sound card, without TTY modem. A simple interface between sound card and phone line or acoustic connection with phone handset are used.
Together with "Virtual Audio Cable" software CallTTY can work via Skype Internet-phone, without additional hardware at all.
You may want to check out more software, such as USRobotics Cordless Skype Dual Phone, PCTalker or Cordless DUALphone Suite, which might be related to CallTTY.