FWD describes the forward message path and rev describes the reverse message path; the latter is optional.

fwd描述转发消息路径，rev描述反向消息路径；后者是可选的。

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Forward: Press FWD key, conveyor forward, the top of the green indicator light.

前进：按下fwd键，传送带前进，上方绿色指示灯亮。

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