Patent ID: 8885760

Claim:
A method for signal transmission between a first and a second system, wherein the first and the second system connected with one another via a current loop, a direct current signal is transmitted in a first frequency range from 0-30 Hz and an alternating current signal is transmitted in a second frequency range from 100-10000 Hz via the current loop, the direct current signal and the alternating current signal are superimposed, wherein the direct current signal and alternating current to be set in the current loop are encrypted in a digital manner, the alternating current signal is used for digital signal transmission and the direct current signal is used for analog signal transmission, comprising the steps of: producing by means of a control unit, said first data stream, in which the direct current signal and the alternating current signal to be set in the current loop are digitally encrypted; transmitting the first data stream to an electrical current output circuit; and converting the transmitted first data stream by the electrical current output circuit into an electrical current signal, wherein: the electrical current signal is composed of the superimposed direct current signal and alternating current signal, or that the transmitted first data stream is converted by the electrical current output circuit into the direct current signal and the alternating current signal; and the electrical current signal or the direct current signal and the alternating current signal are set in the current loop.