A replica of the Pharos Project was created by the Logopolitans through Block Transfer Computation. They intended to use it to relay signals that would keep the CVEs open of their own accord and thus release the Logopolitans from having to keep the CVEs open themselves. The CVEs were necessary to the survival of N-Space by opening what would otherwise be a closed system and thus prevent entropy within N-Space reaching a level at which all matter would crumble.
After the destruction of Logopolis, the Fourth Doctor, Tegan and the Master took circuits from the Logopolitan replica of the Pharos computer room to the original antenna on Earth. By transmitting the Logopolitan program from the Earth antenna the Doctor and the Master were able to stabilise one CVE in alignment with the constellation Cassiopeia. The Master intended to hold the universe hostage by threatening to close the CVE permanently using the Earth antenna if the peoples of the universe did not submit to his will. The Master's plan was foiled when the Doctor disabled the antenna, falling to his death in the process. (TV: Logopolis)