A method of protecting a control signal provided to a field device in a process control system, the method comprising: providing a host station; communicatively coupling the host station to a plurality of input output I/O cards including a first card and a second card, wherein operation is selectively switched from the first card to the second card; communicatively coupling a control signal protection device to the input output I/O cards and to the field device via a control signal loop, wherein the control signal protection device comprises an input terminal (212, 402a) connecting the control signal protection device to the input output I/O cards and an output terminal (214, 404a) connecting the control signal protection device to the field device; providing a control signal for the field device from the host station via the first card or the second card to the control signal protection device, wherein the control signal protection device: (i) stores electric energy, that is extracted from the control signal loop, in a power storing element (414, 416) in a first operational mode; and (ii) supplies electric energy stored in the power storing element (414, 416) to the output terminal (214, 404a) of the control signal protection device in a second operational mode, to sustain the control signal at the output terminal (214, 404a) of the control signal protection device; causing the control signal protection device to switch from the first operational mode to the second operational mode during a transition of operation from the first card to the second card in response to detecting a drop in output current of the control signal protection device. providing a host station; communicatively coupling the host station to a plurality of input output I/O cards including a first card and a second card, wherein operation is selectively switched from the first card to the second card; communicatively coupling a control signal protection device to the input output I/O cards and to the field device via a control signal loop, wherein the control signal protection device comprises an input terminal (212, 402a) connecting the control signal protection device to the input output I/O cards and an output terminal (214, 404a) connecting the control signal protection device to the field device; providing a control signal for the field device from the host station via the first card or the second card to the control signal protection device, wherein the control signal protection device: (i) stores electric energy, that is extracted from the control signal loop, in a power storing element (414, 416) in a first operational mode; and (ii) supplies electric energy stored in the power storing element (414, 416) to the output terminal (214, 404a) of the control signal protection device in a second operational mode, to sustain the control signal at the output terminal (214, 404a) of the control signal protection device; causing the control signal protection device to switch from the first operational mode to the second operational mode during a transition of operation from the first card to the second card in response to detecting a drop in output current of the control signal protection device.