A footswitch is used for easy operation and multi-bends in different Angle can be made continuously by this footswitch.

方便操作的脚踏开关，只要脚踏开关即可完成不同角度的连续弯曲。

youdao

The back of the S4 is pretty much what you'd expect: a couple of spare sets of RCA stereo inputs, a mic input, TRS and RCA outputs, a MIDI passthrough, and a footswitch jack if you're into that sort of thing.

ENGADGET: Native Instruments Traktor Kontrol S4 review Alt