A forced spectrum communication initiating
Forced spectrum communication was a way of forcing viewscreen communications, even though the receiving party did not open their visual channels. As Data opined, though, its results were "spotty at best"; extremely poor visual quality was often the result.
In 2365, William T. Riker ordered forced spectrum communication with the Pakled ship Mondor during the negotiations to return Geordi La Forge to the USS Enterprise-D. (TNG: "Samaritan Snare")