A voice-transit conductor is a communications system used on the planet Kataan during the last years of the planet's life, shortly before its sun went nova.
When Captain Jean Luc Picard relived Kamin's life, he wanted to send a message to another community as soon as he awakened in the other man's life. His wife Eline told him that this could be arranged, he had to wait until the next morning, however. (TNG: "The Inner Light")