Hyperfrequency
A hyperfrequency was a frequency in which audio or visual communications were conducted. 

In 2399, from Coppelius Station on Coppelius, Jean-Luc Picard unsucessfully attemped a secured hyperfrequency transmission to Starfleet Command, informing them he had a first contact situation and requesting permission for establishing diplomatic negotiations and protecting the androids of the planet from a Romulan attack. ()
Mathematics
Communications technology