Asus P5SD2-A - Manual (Page 24)

11. Chassis intrusion connector (4-1 pin CHASSIS)
This connector is for a chassis-mounted intrusion detection sensor or switch. Connect
one end of the chassis intrusion sensor or switch cable to this connector. The chassis
intrusion sensor or switch sends a high-level signal to this connector when a chassis
component is removed or replaced. The signal is then generated as a chassis intrusion
event.
By default , the pin labeled “Chassis Signal” and “ Ground” are shorted with a jumper
cap. Remove the jumper caps only when you intend to use the chassis intrusion
detection feature.
12. Digital Audio connector (4-1 pin SPDIF_OUT)
This connector is for the S/PDIF audio module to allow digital sound output. Connect
one end of the S/PDIF audio cable to this connector and the other end to the S/PDIF
module.
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