RFM modulator portapack
An RFM modulator portapack was a portable Starfleet communications tool that could alter a signals electromagnetic frequency.

The modulator could be carried in a backpack, with a monitor display that flipped up on top and eight pairs of dial controls. The monitor displayed communications uplink status, range,  and frequency.

In 2257, the  sent an away team with an RFM modulator portapack to the planet Pahvo, in an effort to modify the Pahvan transmitter to detect Klingon cloaked ships "as a kind of SONAR." ()
Communications technology