 Then fifteen minutes precisely were allowed to elapse, during which time the instrument at the first station was put in circuit with both wires while the opposite one was detached from its upper wire, thus reversing the arrangements at each station.At the expiration of the fifteen minutes the message or signals came in to the initial station, a perfect duplicate of those sent from it, as by previous agreement.And although no 'transmitting key' was made use of, nor any 'sounder' to voice the messages, yet they were just as exact and distinct as any that ever traveled over a metallic conductor.