A switch may include a movable board and a pole board having an inner surface on which a fixed contact point is exposed, the inner surface facing the movable board. A movable contact point may be supported by the movable board and may include a plurality of contact pieces making resilient contact with the inner surface of the pole board. The switch may also include an output terminal corresponding to the fixed contact point. The movable contact point and the fixed contact point may come in contact with each other when a position of the movable contact point is changed via a displacement of the movable board. The fixed contact point and the output terminal may be connected via a board having a disconnection detection circuit. The board may be enclosed in an insulating seal material.

In an inhibiter switch, a detent plate may be rotated on one side around a rotational shaft to be assembled in a pole board, and a stopper may be provided in the pole board to define a rotation range of the detent plate on the one side. An interference portion may be provided on a movement track of a movable contact piece when the detent plate rotates around the rotational shaft, wherein the interference portion may interfere with the movable contact piece to become resistance to rotation of the detent plate to the other side around the rotational shaft.

An inhibiter switch is configured to include a fixed contact point that is connected to and disconnected from a movable contact point. The movable contact point is configured to make pressure contact with the fixed contact point by the movement of a movable board by a shaft member, wherein a press-fit amount of the shaft member to a projecting portion is made smaller toward a connecting portion between the projecting portion and an inner periphery of an insert hole of the movable board.

A switch comprising a body case, a movable board that is movably disposed in the body case and a movable contact point disposed in the movable board is disclosed. A fixed contact point is provided in the body case with a lubricating agent applied thereto. The movable contact point makes pressure-contact with the fixed contact point, and is connected and disconnected from the fixed contact point corresponding to a position of the movable contact point changing by moving the movable board. Grooves are formed in a contact portion of the movable contact point with the fixed contact point to be arranged along the movement direction of the movable contact point.

A rotary selector switch prevents accidental rotation to an undesired position. For example, an automobile moving forward at 55 kph may have a rotary selector switch in electrical communication with its transmission. The disclosed switch prevents accidental rotation that would indicate that a REVERSE gear is desired when it is not. Optionally, on override feature may permit users to overpower an otherwise prevented rotation.

In an inhibiter switch, a detent plate may be rotated on one side around a rotational shaft to be assembled in a pole board, and a stopper may be provided in the pole board to define a rotation range of the detent plate on the one side. An interference portion may be provided on a movement track of a movable contact piece when the detent plate rotates around the rotational shaft, wherein the interference portion may interfere with the movable contact piece to become resistance to rotation of the detent plate to the other side around the rotational shaft.

Provided are a maintenance-free gas density relay and a mutual check method therefor. The maintenance-free gas density relay includes a gas density relay body and first gas density detection sensors which are in communication on gas paths, and an intelligent control unit connected to the gas density relay body and the first gas density detection sensors separately, where the intelligent control unit compares and checks a first pressure value and a second pressure value acquired at the same gas pressure, and/or compares and checks a first temperature value and a second temperature value acquired at the same gas temperature, or compares and checks a first density value and a second density value acquired at the same gas density, and can further upload received data to a background for data comparison by the background. The present disclosure further completes online self-check or mutual check of the gas density relay while being used for monitoring gas density of a gas-insulated or arc-control electrical apparatus, thereby improving efficiency, avoiding maintenance, reducing cost, and ensuring safe operation of a power grid.