The invention relates to a method for signal transmission between a first and a second system (S1, S2) that are interconnected by means of a current loop (L). A direct current signal is transmitted in a first frequency range (AB) and an alternating current signal in a second frequency range (DB) via the current loop (L). The direct current signal and the alternating current signal are superimposed, the alternating current signal being used for digital signal transmission and the direct current signal being used for analog signal transmission. A control unit (CPU) produces a first data flow (U1) in which the direct current signal and the alternating current signal to be adjusted in the control loop (L) are digitally encoded, the first data flow (U1) being transmitted to a current output circuit (S), and the transmitted first data flow (U1) being converted into a current signal by the current output circuit (S), the current signal consisting of the superimposed direct current signal and alternating current signal, or the current output circuit (S) converts the transmitted first data flow (U1) into the direct current signal and the alternating current signal. The current signal or the direct current signal and alternating current signal are adjusted in the current loop (L).