Each of 170 channels is one MIT OpenCourseWare course looping lecture after lecture, with a program guide, a red now-line and a channel-number keypad (type 18.6 to tune). The schedule is invented, but it is shared, so everyone who tunes in lands on the same lecture. Lectures stream from MIT’s own YouTube channel under CC BY-NC-SA, with captions and a link to the course notes. Unofficial.