Abstract: An indicator circuit for indicating the states of various electric components such as limit switches, comprising a light emitting device such as a light emitting diode, and a constant current device, such as a constant current diode, connected in series with the light emitting element. The constant current element significantly expands the operable range of the input voltage to the indicator circuit, and keeps the brightness of the light emitting device constant over a wide input voltage range. For high voltage applications, a plurality of constant current devices may be connected in series, and, preferably, balancing resistors and/or zener diodes may be connected in parallel with them.

Abstract: A limit switch includes a casing, a switch mechanism housed in the casing, a cover covering the casing, and an actuator mounted in the casing for operating the switch mechanism, the cover having a curved or partly spherical convex surface. The cover has at least a transparent or semitransparent portion, and a rating plate is disposed against a back of the transparent or semitransparent portion of the cover. The curved or partly spherical convex surface of the cover prevents spatter expelled from a welding machine from being deposited thereon. Since the spatter is not deposited directly on the rating plate, indications on the rating plate and the energization of an operation indication lamp within the cover can reliably be confirmed.