"Assuming no one ever wants to talk to anyone else."
The psi block is a Terran Dominion technology designed to use sigma radiation to slow the speed and reaction time of nearby zerg organisms. These devices are small enough to deploy into the suits of individual terran infantry. Its design was based on the psi disrupter research of the United Earth Directorate. They have a range of fifty to one hundred and fifty meters.
Psi blocks were first deployed in 2511 during the One-Day War on Gystt, where an expedition of Terran Dominion forces sent to investigate the planet were given use of the devices. While they were able to slow down zerg forces, they also blocked communications, and did not seem to be effective against chitha that they were forced to engage.