Abstract: This invention relates to fault detection in electrical circuits, in particular it relates to fault detection for a plurality of adjacent input circuits. The invention provides a method and apparatus for detecting a control or communication fault on an analogue circuit by simulating said analogue circuit using a simulated circuit comprising digital circuit components; the simulated circuit receiving a control input to provide a first output; and the analogue circuit receiving said control input to provide a second output; and setting an error condition when the first output and the second output differ.

Abstract: A power supply that is capable of supplying power to an input/output channel for an Industrial Process Control System. The power supply includes a primary voltage converter having a first voltage input and a second voltage output, and overvoltage protection components that prevent the second voltage from rising above a predetermined maximum. The power supply includes a first low dropout regulator that is connected to receive the second voltage and to generate a third voltage, a second low dropout regulator that is connected to receive the second voltage and to generate a fourth voltage, and a third low dropout regulator that is connected to receive the fourth voltage and to generate a fifth voltage. The power supply provides an over-voltage fault tolerant self-testable architecture, allows for compact low cost individual channel isolation and fault tolerant EMI/RFI filtration.

Abstract: The present invention includes a contact block for a safety switch that has a support structure and a pair of electrical contacts that are fixed in position on the support structure. The contact block includes a contact block plunger provided with a bridging contact. The bridging contact extends through the contact block plunger, from one side to another, and protrudes from the sides of the contact block plunger. The contact block plunger is moveable in-between the fixed pair of electrical contacts to move the bridging contacts into and out of contact with the fixed pair of electrical contacts. A contact block guide extends along the support structure and between the pair of fixed electrical contacts and cooperates with the contact block plunger such that the contact block plunger is restricted to movement along the contact block guide.

Abstract: A safety switch for affecting the operating state of equipment to which the safety switch is at least indirectly connected. The safety switch includes a configuration, such as a number of contacts, that is arranged to change from a first condition to a second condition depending on whether or not an actuator has been engaged with or disengaged from the safety switch. The safety switch includes an arrangement for determining information that is at least indicative of an operational property of the configuration, and for storing information that is at least indicative of the obtained information.

Abstract: A safety switch configured to determine whether a magnetically operated switch which forms part of the safety switch has been welded closed. The safety switch is configured to establish a first magnetic field in the vicinity of the magnetically operated switch. The magnetic field is arranged to move the magnetically operated switch from a first configuration to a second configuration. The safety switch monitors the state of the magnetically operated switch to determine if the magnetically operated switch has been moved by the first magnetic field, thereby determining if the magnetically operated switch has been welded closed.

Abstract: There is provided a safety switch having a housing configured to receive a removable key, and a mechanism arranged to be operated when the key is moved from an engaged position to a partially disengaged position, the mechanism being arranged to cause a signal to pass to a separate apparatus, wherein the safety switch further comprises a lock which is controlled by the separate apparatus and is arranged to prevent the key from being fully disengaged from the safety switch until a signal has been received in response from the separate apparatus.

Abstract: A safety switch that includes a housing, a first switch, and a second switch. The switch has a two part rod that is axially moveable within the housing. The parts of the rod are co-operable with respect to one another and independently operable to activate one of the first and second switches. A biasing element is arranged to bias the rod parts into contact with a cam arrangement and arranged to bias the rod parts out of engagement with one of the respective switches. The cam arrangement is configured such that rotation of the cam arrangement will move the rod parts thereby activating the switches to allow the safety switch to conduct electricity.

Abstract: A safety switch plunger includes a moveable conductor which extends transversely through the plunger and protrudes from opposite sides of the plunger. The plunger is provided with a structure that is positionally fixed on the plunger. The structure is positioned such that it is arranged to come into physical contact with and affect the movement of the moveable conductor when the moveable conductor and plunger are moved relative to one another thereby providing a fail-to-safe safety switch.

Abstract: A safety switch assembly having a handle pivotably attached to a casing to allow selective operation of an electrical contact assembly. The handle is attached to the casing with a movable pivot such that excessive grip pressure renders the safety switch inoperable until the safety switch is reset. The handle is moveable responsive to grip pressures that range from no actuation to a first grip pressure. Actuation of the handle in this range controls operation of the electrical contact assembly. Gripping of the switch with a grip pressure greater than the first grip pressure moves the pivot such that the safety switch is rendered inoperable, or non-conductive, until manipulation of a reset actuator returns the pivot to a pivot position associated with the first operating zone. Such a construction provides a safety switch that can be rendered inoperable and reset to allow subsequent operation.

Abstract: A safety switch assembly includes a body constructed to be mounted in a support structure and generally enclose the operative structure of the safety switch. The safety switch assembly includes an actuator constructed to pass through one of the support structure or the base to operatively engage the operative structure of the safety switch to control the safety switches electrical orientation to communicate or terminate communication of electrical power to a device equipped with the safety switch.

Abstract: A safety arrangement for use with a piece of equipment. The safety arrangement includes a signal generating unit for generating an optical signal, an elongate element, and a signal detecting unit. The elongate element is disposed along, about, around or through the piece of equipment and is capable of transmitting an optical signal. The signal detecting unit detects an optical signal. The signal generating unit is connected to the signal detecting unit by the elongate element such that the signal detecting unit is in optical communication with the signal detecting unit. The signal detecting unit is arranged to detect a change in the optical signal transmitted by the elongate element as a consequence of movement of the elongate element and, upon detection of the change in the signal, the detecting unit is configured to effect a change in the operation of the piece of equipment.

Abstract: A safety switch includes a cable having a first end connected to a cable translator moveable between a disengaged position and an engaged position, the cable having a second end for connection to a remote lock and power supply switch.

Abstract: A mounting arrangement includes a first mounting that is attachable to a first support structure and configured to cooperate with one of a safety switch and a safety switch actuator and a second mounting configured to cooperate with the other of the safety switch and the safety switch actuator. The first and second mountings provide variable guided interaction between the first and second mountings and thereby provided variable guided interaction between the safety switch and the safety switch actuator.