Page "Radioteletype" Paragraph 39

Most of the terminal unit equipment used for receiving RTTY signals was homebuilt, using designs published in amateur radio publications.

These original designs can be divided into two classes of terminal units: audio-type and intermediate frequency converters.

The audio-type converters proved to be more popular with amateur radio operators.

The Twin City, W2JAV and W2PAT designs are examples of typical terminal units that were used into the middle 1960s.

The late 1960s and early 1970s saw the emergence of terminal units designed by W6FFC, such as the TT / L-2, ST-3, ST-5, and ST-6.

These designs were first published in RTTY Journal starting in September 1967 and ending in 1970.