Unidirectional

Compare unidirectional mass media such as radio and television with bidirectional ones such as correspondence and the Internet.

[...] a reversible booster was fitted to the trailing bogie; all previous applications on the L.N.E.R. for use in main line traffic had been of unidirectional boosters, […]

Equally important is the class mailing list, which facilitates two-way communication at a distance. (By contrast, the web page is basically a unidirectional teacher-to-student communication.)