Abstract: A method and an apparatus are provided for data transmission between a transceiver located in a drill hole and an above ground transceiver which are connected together by a two-wire line composed of an armoured, insulated copper core cable. The data are transmitted between the two transceivers via the two-wire line by successive, essential current-carrying time intervals. In the current-carrying time intervals, the portion of the transmitted energy is stored in the transceiver located in the drill hole, being stored therein for the current-free time intervals. The data are transmitted from the transceiver located in the drill hole to the transceiver disposed above ground by interrupting the current flow in the two-wire line or by short-circuiting the ends of the two-wire line, and are transmitted in the reverse direction by interrupt current feed of the two-wire line.