(Bloomberg) -- AMS AG, a Switzerland-based maker of light sensors for smartphones, became at least the fourth key Apple Inc. supplier this week to reduce revenue estimates for the current quarter.

The company, which generates the majority of its revenue by selling parts to Apple, said Wednesday it’s projecting fourth-quarter sales of $480 million to $520 million. Last month, the company gave a forecast of $570 million to $610 million.

AMS said the reduction is due to “recent demand changes from a major consumer customer,” a similar explanation to those offered by Qorvo Inc., Lumentum Holdings Inc. and Japan Display Inc. earlier this week when they, too, unexpectedly reduced their outlooks.

AMS makes what is known as an ambient light sensor, which helps measure how far a phone is from a user, for the Face ID facial recognition system on Apple’s iPhones. Qorvo makes wireless chips, while Lumentum makes 3D laser sensors for Face ID. Japan Display makes smartphone screens.

None of the companies specifically cited Apple as the customer that reduced its need for components, but Apple is the largest customer and biggest revenue driver for all four, according to data compiled by Bloomberg. Qorvo gets 36 percent of revenue from Apple, Lumentum generates 30 percent, AMS receives more than 20 percent and Japan Display gets 55 percent.

The Cupertino, California-based technology giant likes to diversify its suppliers, but four major component makers reducing revenue forecasts in the same week could mean Apple is bracing for lower than expected sales of its latest devices.

To contact the reporter on this story: Mark Gurman in San Francisco at mgurman1@bloomberg.net

To contact the editors responsible for this story: Tom Giles at tgiles5@bloomberg.net, Andrew Pollack, Mark Milian

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