The factory are specially producing S terminal and A&Vcomposite-Boards, GQ fiber socket, RCA pin jack, WP exterior connector outlet, USB plug, Connectors etc.

我厂主要生产S端子、音视频组合板、GQ光纤、RCA同芯插座、WP外接线插座、USB插头、连接器等系列。

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