The equipment is still at the experimental stage.

这种设备仍处于试验阶段。

《牛津词典》

These are still in the experimental stage.

这些都是仍然在实验阶段。

youdao

The technique is still at the experimental stage.

这项技术正处于实验阶段。

youdao

The new method is promising, he said, but it is still at an experimental stage.

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Time will tell whether they can take OneID beyond the experimental stage and turn it into a significant enterprise.

FORBES: Vinod Khosla Bets Millions on One Digital Identity

Lots of people have volunteered for the service's experimental stage, so Google is expected to make it more widely available soon.

ECONOMIST: Now they have assumed power, what will consumers do with it?