A safety circuit for fail-safe shutdown of a dangerous technical system with a plurality of disconnectable system component groups comprises a plurality of safety switching devices electrically connected to one another in series to form a closed-loop monitoring circuit in which electric monitoring current flows through the safety switching devices. Each of the safety switching devices includes: a fail-safe control unit that detects and evaluates information about a current operating state of any system component group assigned to it; and a current flow adjuster that changes the current flow within the monitoring circuit to interrupt the monitoring circuit in response to detection of a safety command by the safety switching device. The fail-safe control units generate a shutdown signal in response to an interruption of the current flow within the monitoring circuit, which causes the fail-safe shutdown of any of the system component group not already shut down.

A battery pack includes a main switch configured to electrically connect a battery module and a load, a power supply configured to supply driving power to the main switch, and a power blocking device configured to block the driving power based on a current flowing between the battery module and the load.

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 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.

Systems (100) and methods (600) for controlling operations of a Handheld Scanning and Deactivation (HSD) device. The methods comprise: determining whether a human is located within a defined distance range of the HSD device; preventing first operations from being performed by the HSD device which cause a magnetic field to be generated, if it is determined that said human is located within the defined distance range of said HSD device; and initiating the first operations if it is determined that the human is not located within the defined distance range of the HSD device. The first operations comprise (1) interrogation operations for detecting a presence of an electronic article surveillance security tag and/or (2) deactivation operations for deactivating an electronic article surveillance security tag.

A relay control apparatus for a relay including a contact connected between a positive electrode of a battery and a load, and a coil connected between a relay power terminal and a ground in which the contact moves to a closed position when the coil is energized. The relay control apparatus includes a coil control switch which is turned on in response to a first switching signal having a voltage level that is equal to or higher than a first threshold voltage in response to a relay on-command, and a relay holding circuit configured to store emergency power using power supplied from the battery.

An apparatus including one or more relays and a fault detector is disclosed. The one or more relays are coupled to a load. The fault detector is coupled with the one or more relays and receives at least one control signal. The fault detector includes a sensor to detect electricity flowing through the load and generate a detection signal. Based on a comparison of the control signal and the detection signal, the fault detector generates a fault signal indicative of whether a relay is functional or faulty.

An apparatus for detecting faults in devices, the apparatus comprising a first input for receiving a first control signal for controlling a switch, a first output for providing the first control signal to the switch, a sensor to detect a presence and an absence of electricity flowing through a load controlled by the switch to generate a detection signal, and circuitry configured to compare the detection signal and the first control signal and generate a fault signal indicating whether a fault is detected. When a logic level of the detection signal is the same as a logic level of the first control signal, the fault signal indicates that the fault is not detected. When the logic level of the detection signal is different from the logic level of the first control signal, the fault signal indicates that the fault is not detected.

A relay control apparatus for a relay including a contact connected between a positive electrode of a battery and a load, and a coil connected between a relay power terminal and a ground in which the contact moves to a closed position when the coil is energized. The relay control apparatus includes a coil control switch which is turned on in response to a first switching signal having a voltage level that is equal to or higher than a first threshold voltage in response to a relay on-command, and a relay holding circuit configured to store emergency power using power supplied from the battery.