A slow, letter-quality printing device and terminal based on the IBM Selectric typewriter. The print head was a little sphere resembling a golf ball, bearing reversed embossed images of 88 different characters arranged on four parallels of latitude; one could change the font by changing the golf ball. The device communicated at 134.5 bits per second, half duplex. When the computer transmitted, it physically locked the keyboard.
This was the technology that enabled APL to use a non-EBCDIC, non-ASCII, and in fact completely non-standard character set. This put it 10 years ahead of its time - where it stayed, firmly rooted, for the next 20, until character displays gave way to programmable bit-mapped devices with the flexibility to support other character sets.