LCH, I haven't heard of this. However, GND means grounding, that is to say, the negative line of the speaker, the black one. LIN indicates whether the audio signal is input in the left channel or the right channel, and LIN does not know whether it is input in the left channel or the right channel. Rin doesn't know whether it's the left channel or the right channel. Slb doesn't know what it means, and neither does sla. That's all I know, hehe