Communing was a process available to lawgivers on Beta III, before Landru destroyed itself. It was a telepathic exchange between the lawgiver and his mechanical master, and was considered a desirable state by lawgivers. While communing, lawgivers were largely unresponsive to external stimuli, in one instance enabling the escape of the landing party.
Lawgivers communed regularly, and could also initiate the state when they encountered a situation they did not understand. In short order, Landru could receive and evaluate the circumstances, and issue new instructions, either to the lawgiver, or to other members of the Body. (TOS: "The Return of the Archons")