A safety switching device for fail-safely switching on and off an electrical load, and to a system comprising at least two safety switching devices which interact in a fail-safe manner via a single-channel. The safety switching device comprises a fail-safe control unit, a first and a second electronic switching element connected with a first and a second output terminal; and at least one input terminal for receiving a first switching signal that causes a switching of said switching elements. Said first and second switching elements each comprise an output which provides depending on the first switching signal an output signal having a first or second potential. A third output terminal connects said safety switching device to a second safety switching device, providing a clocked signal depending on the first switching signal and being monitored by said control unit for performing a cross fault detection.

A safety switching apparatus for switching-on or switching-off a technical installation has a first input for receiving a first clock signal via a feed line, said first clock signal having a first clock frequency. A failsafe control/evaluation unit processes the first clock signal in a failsafe manner in order to generate an output signal for switching-on or switching-off the technical installation in response to the first clock signal. A clock reference provides a second clock signal having a second clock frequency. A current-increasing circuit having a switching element is arranged for selectively increasing an input current into the first input. The switching element is coupled to the clock reference and selectively activates or deactivates the current-increasing circuit in response to the second clock frequency.

A safety switching device for driving a plurality of different kinds of guard locking devices is provided. The safety switching device comprises a first terminal and a second terminal for connecting a guard locking device, and a safety processor adapted for controlling drive signals at the first and the second terminal to drive the guard locking device. The safety processor is adapted for determining a kind of a guard locking device connected to the first and/or the second terminal out of a plurality of different kinds of guard locking devices by detecting external electrical connections between the first terminal, the second terminal, and a reference potential. The safety processor is further adapted for controlling the drive signals depending on the determined kind of the guard locking device.

A circuit breaking system includes an output device for outputting an output signal; a control device controlled by the output signal; a power input terminal provided in the output device, for supplying power to the control device; a power supply to the output device, which has a ground terminal; a break circuit disposed between a power output terminal and the power input terminal; a switching circuit disposed between the break circuit and the power output terminal; and a short circuit disposed between a ground and a node which connects the power input terminal and the break circuit. The break circuit and the short circuit are operated so as to not be closed at the same time. When the switching circuit is closed, the break circuit is closed while the short circuit is open. When the switching circuit is open, the break circuit is open while the short circuit is closed.

A relay circuit and a method for performing a self-test. The relay circuit has four relays, each relay having a first forcibly guided contact and a second forcibly guided contact. The four relays are arranged in a first and a second pair of two in series connected first forcibly guided contacts. The first and second relay pair are arranged in parallel between a power supply connection and a load connection for switching a power supply to a load through the first forcibly guided contacts. Such a relay circuit enables supplying power via one of the relay pairs, while cutting power via the other relay pair, which facilitates testing of the relay pair which has cut power without interrupting the process supervised by the Safety Instrumented System which the relay circuit forms part of.

Aspects of the present disclosure involve systems, methods, and the like, for an automatic transfer switch (ATS) of a power system. The ATS allows for switching between two or more power systems while preventing back-feeding of the power systems. To provide the safety features of the ATS, a safety circuit and control board may be implemented with the magnetic latching relays to control the actions of the latching relays and provide the switching function of the ATS. In one particular embodiment, the safety board comprises one or more electromechanical relays positioned between the controlling electronics of the control board and the magnetic latching relays. The safety board design contains measures to ensure it still functions if one of the disconnect switches is not connected, if one of the connections to a first load phase, a second load phase or neutral is lost and if the main control board is not connected.

An object is to provide a relay module and a relay terminal block enabling reduction of the workload of a worker and realization of space saving. The relay terminal block is provided with a plurality of relay modules and a select signal generation device, and each relay module is provided with a selective signal transmission device. A plurality of input signal transmission wires are connected to each relay module. One input signal transmission wire is selected according to a select signal output from the select signal generation device, and a signal input to the selected input signal transmission wire is output via an output signal transmission wire. Further, the relay terminal block is provided with an input/output module and is capable of outputting signals input from the plurality of the input signal transmission wires as serial signals.

An object is to provide a relay module and a relay terminal block enabling reduction of the workload of a worker and realization of space saving. The relay terminal block is provided with a plurality of relay modules and a select signal generation device, and each relay module is provided with a selective signal transmission device. A plurality of input signal transmission wires are connected to each relay module. One input signal transmission wire is selected according to a select signal output from the select signal generation device, and a signal input to the selected input signal transmission wire is output via an output signal transmission wire. Further, the relay terminal block is provided with an input/output module and also is capable of outputting signals input from the plurality of the input signal transmission wires as serial signals.