Advantech AIMB-742 - Line Out, MIC in Connector (CN55); Audio Input from CD-ROM (CD IN; CN56); Aux Line-In Connector (aux IN; CN57)

AIMB-742 User’s Manual 26
2.16 Line Out, Mic IN connector (CN55)
The Line Out is to output the audio signal to external audio device, like
speakers or headphones. The Mic IN is to input the audio signal via
microphones.
2.17 Audio input from CD-ROM (CD IN; CN56)
The CD IN is a connector for CD-ROM to input the audio signal.
2.18 Aux Line-In connector (AUX IN; CN57)
The connector is for audio device with Line-in connector.