An interface device (100, 200), comprising: a field circuit, a barrier included by a boundary, whereas the field circuit is disposed on a field side of the barrier, the field circuit configured to receive a field signal from a field device (1a-f) in one of a digital and analog format, the field circuit including: a first section (100a, 200a, 300a) and a second section (100b, 200b, 300b); the first section (100a, 200a, 300a) is a control circuit that interfaces with controllers or devices on the control side of the boundary; the second section (100b, 200b, 300b) is a field circuit that interfaces with field devices on the field side of the boundary; only one digital-to-analog converter included in the first section (100a, 200a, 300a) configured to drive an output signal to the field device (1a-f); only one analog-to-digital converter included in the second section (100b, 200b, 300b) configured to perform a conversion of the field signal on the field side of the barrier to generate a converted signal; and a processing circuit included in the first section (100a, 200a, 300a) configured to split the converted signal at the output of the analog-to-digital converter in two signal paths, a data stream and a digital input value both inputted to a multiplexer included in the first section (100a, 200a, 300a), from the converted signal, characterized in that the processing circuit is further configured to: transmit signals from each of the two signal paths to the controllers or devices disposed on the control side of the barrier, and the first section (100a, 200a, 300a) including a demultiplexer configured to separate one time-multiplexed digital channel into data including a data stream and a digital output value data-stream to the second section (100b, 200b, 300b), whereas the data stream is fed to a modulator configured to convert to a Frequency Shift Keying, FSK, signal. a first section (100a, 200a, 300a) and a second section (100b, 200b, 300b); the first section (100a, 200a, 300a) is a control circuit that interfaces with controllers or devices on the control side of the boundary; the second section (100b, 200b, 300b) is a field circuit that interfaces with field devices on the field side of the boundary; only one digital-to-analog converter included in the first section (100a, 200a, 300a) configured to drive an output signal to the field device (1a-f); only one analog-to-digital converter included in the second section (100b, 200b, 300b) configured to perform a conversion of the field signal on the field side of the barrier to generate a converted signal; and a processing circuit included in the first section (100a, 200a, 300a) configured to split the converted signal at the output of the analog-to-digital converter in two signal paths, a data stream and a digital input value both inputted to a multiplexer included in the first section (100a, 200a, 300a), from the converted signal, characterized in that the processing circuit is further configured to: transmit signals from each of the two signal paths to the controllers or devices disposed on the control side of the barrier, and the first section (100a, 200a, 300a) including a demultiplexer configured to separate one time-multiplexed digital channel into data including a data stream and a digital output value data-stream to the second section (100b, 200b, 300b), whereas the data stream is fed to a modulator configured to convert to a Frequency Shift Keying, FSK, signal.