The Vistior sleeper known as John May was provided with a comms device when he infiltrated the planet Earth and masqueraded as a Human. He proved to be the first Visitor to be infected by Human emotion and he instead sought to protect his family thus spawning the creation of the Fifth Column. John May kept in contact with these defectors by use of a comms device in his possession which he hid amongst the various items he owned. He was later killed by Ryan but the communication sphere remained hidden and was known to Fifth Column that lived onboard the Motherships such as Joshua. (John May)
When Ryan infiltrated the New York Mothership, he encountered Joshua and the Fifth Column. Before Ryan returned to the surface, he asked Joshua on how he could get into contact with him. The Motherships medical officer revealed that John May had a comms device which was a piece of outdated tech and that the Visitors would not be watching for it. He suggested that Ryan track it down and use it as a means of communicating with Joshua as well as his group. (Pound of Flesh)
Following his return to the surface, Ryan along with his Human comrades journeyed to John May's old residence where they met the defectors step son James May. They later went to a warehouse that stored May's possessions and Ryan uncovered the comms device. He later used this to get into contact with Joshua so that they could find the status of Georgie Sutton who had been captured onboard the New York Mothership. Joshua managed to track down Georgie and allowed the captive Human to speak to his friends where Sutton revealed that he wanted Joshua to kill him so that the Fifth Column's secrets did not get revealed. His final words via the comms device was to Ryan and Father Jack Landry before Joshua administered a compound that killed Georgie. (John May)
The rebel Visitors onboard the Mothership later used the comms device to inform Ryan and the Fifth Column that Anna had deployed a Soldier to track down Valerie Stevens. (Heretic's Fork) Joshua again passed information to Ryan by telling him that Anna intended to deploy a team of Trackers in order to locate the Earth based Fifth Column members. Through this communication link, Ryan managed to get the coding for Visitor Shuttles and used that information to encode an Earth based stinger missle to shoot down the Tracker shuttle. (We Can't Win)
Lisa who knows of Diana's existance and does not want to be caught, gives Diana a Comms Device so the two can speak without Anna finding Lisa in the chamber.