Abstract: A constant-current regulator regulates and monitors the current fed to one or more downstream loads. It also serves to even out the current fed to the downstream load or loads at the control level or when there is a change in the control level. In order to enhance the security and reliability of operation of such a constant-current regulator when installed in a control and monitoring circuit, control signals having a similar regulating/monitoring content are applied to the constant-current regulator by means of two separate busses (3, 4) in a mutually independent manner. The constant-current regulator is used to carry out a separate plausibility/conformity check of the control signals from the first bus (3) and the control signals from the second bus (4). If a lack of plausibility/conformity is ascertained for the control signals of the first bus (3), the control signals of the second bus (4) are taken as the basis for operation of the constant-current regulator.

Abstract: A switch-off device for airport series circuits (2) has input terminals (3, 4) which are connected to a current source (1). It also has output terminals (5, 6) which are connected to a series circuit (2) and connecting elements (7, 8) by means of which the input terminals (3, 4) and the output terminals (5, 6) can be connected to one another. The switch-off device has an actuator (11) for the purpose of simplifying operation and permitting a plurality of different, clearly visible operating states. In a normal position, the actuator positions the connecting elements (7, 8) such that each input terminal (3, 4) is connected to an output terminal (5, 6). In a service position, it positions the connecting elements (7, 8) so that the input terminals (3, 4) are disconnected from the output terminals (5, 6) and are connected to a grounding terminal (9), while the output terminals (5, 6) are connected to one another and to the grounding terminal (9).