A protected switch includes first and second electromechanical relays with guided contacts, each including an electromagnet and electrical contacts. A first contact of the first relay and a first contact of the second relay are connected in series in order to form a switching circuit. The switch further includes an interconnection circuit which connects at least a portion of the other electrical contacts of the first and second relays. The excitation of the first electromagnet is conditional on the state of the second relay and the excitation of the second electromagnet is conditional on the state of the first relay.

A relay arrangement includes at least two series-connected relays, which are mechanically and electrically connected to a main printed circuit board via first terminals and second terminals, and at least one flat conductor for conducting current between the at least two series connected relays. The flat conductor is mechanically connected to the main printed circuit board and electrically and thermally connected to the first terminals of the relays, and the at least one flat conductor is configured to dissipate heat produced during operation of the relays.

A safety switching apparatus for safely switching on an electrical load includes for this purpose, the functionality of two non-forcibly guided changeover switches and, in particular, their normally closed contacts, which can be monitored during a starting process without using a microcontroller. The normally closed contacts are each arranged in a separate diagnostic circuit, which are connected in parallel with respect to a test voltage. The diagnostic circuits are each monitored by a diagnostic current detection device. The excitation coils of the changeover switches can each be short-circuited via a short-circuit device if a diagnostic current continues to flow in the respective diagnostic circuit for a predetermined time period after an activated starting process.

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.

A modular switching contactor arrangement for use in a safety-oriented application, has two switching contactor modules that can be arranged in succession by means of a coupling module, the switching contactor modules and the coupling module merely having to be joined together by a user, without any external wiring, so as to be mechanically and electrically coupled to one another. In the mounted state, the switching contactor arrangement has a reduced construction width that is substantially delimited by the narrow faces of the switching contactor modules. In particular, the construction width can be 22.5 mm.

A relay arrangement includes at least two series-connected relays, which are mechanically and electrically connected to a main printed circuit board via first terminals and second terminals, and at least one flat conductor for conducting current between the at least two series connected relays. The flat conductor is mechanically connected to the main printed circuit board and electrically and thermally connected to the first terminals of the relays, and the at least one flat conductor is configured to dissipate heat produced during operation of the relays.

To enable an increase in a service life of a modular safety relay circuit, a modular safety relay circuit is provided for the safe switching on and/or off of at least one machine comprising at least one relay module to which the at least one machine is connected, wherein the relay module comprises at least two relay contacts that are connected in series and that can be brought from a first position into a second position and vice versa; and wherein one relay contact switches in advance by a delay of the other relay contact; and a control unit controlling the relay contacts that alternatingly controls the relay contacts in accordance with a state detection of the relay contacts with the delay.

A safety circuit coupled between a first direct current (DC) circuit and a second DC circuit, wherein the first DC circuit supplies power to the second DC circuit. The safety circuit comprises a first series connection between positive poles of the first and second DC circuits (the first series connection comprising a first diode, a second diode and a first controllable switch), a second series connection between negative poles of the first and second DC circuits (the second series connection comprising a third diode, a fourth diode and a second controllable switch), a first energy storage device (coupled between the positive pole of the second DC circuit and the first terminal of the second controllable switch), and a second energy storage device (coupled between the negative pole of the second DC circuit and the first terminal of the first controllable switch). The safety circuit further comprises a first feedback circuit for indicating an active state of the first controllable switch and a second feedback circuit for indicating an active state of the second controllable switch.

A modular switching contactor arrangement for use in a safety-oriented application, has two switching contactor modules that can be arranged in succession by means of a coupling module, the switching contactor modules and the coupling module merely having to be joined together by a user, without any external wiring, so as to be mechanically and electrically coupled to one another. In the mounted state, the switching contactor arrangement has a reduced construction width that is substantially delimited by the narrow faces of the switching contactor modules. In particular, the construction width can be 22.5 mm.

For providing a very simple and reliable monitoring of the functionality of contacts together with a high flexibility of selection of the contacts a method for monitoring the functionality of redundantly interconnected contacts is provided, preferably within a load current circuit, wherein said n contacts, n=2, provide an electrical connection between a power supply and a load, wherein said n contacts are switchable by a controller and wherein each of said n contacts is designed for providing the electrical connection between the power supply and the load all alone. The method is characterized in that the controller switches on said n contacts during n subsequent activations according to a defined schedule according to which at the first of said n subsequent activations one of said n contacts is switched on first and the remaining n1 contacts are switched on afterwards, so that a verification regarding the functionality of said one of said n contacts is possible, and according to which at each of the n1 remaining subsequent activations a further one of said n contacts is switched on first with switching on of the remaining n1 contacts afterwards, so that after said n subsequent activations each of said n contacts has once been switched on first and a verification regarding the functionality of each of said n contacts is possible. Further, a corresponding method for subsequent deactivations and corresponding apparatuses are provided.