With an Ohm meter, I mapped the internal interface from the double USB Header Adapter (both) on the Dell Front Panel and found the following (updates in red in the table below).

FNT_PNL (http://www.lnmdesign.com/400sc/front_pnl.html)

From the pin-side:

Pin Description Connects to My Mapping Choices
1 INTRUDER 3 INTRUDER 3, FNT 32
2 VCC +5v FNT 3, FNT 4 (USB red1, red2) Motherboard USB Header - Pin 1
3 VCC +5v FNT 2, FNT 4 (USB red1, red2) Motherboard USB Header - Pin 2
4 VCC +5v FNT 2, FNT 3 (USB red1, red2)
5 LED VCC CTRL 6 thru R19, CTRL14 thru R20
6 ?  
7 ?  
8 INTRUDER 5 INTRUDER 5
9 GND GND (USB black1, black2, shield) Motherboard USB Header - Pin 7
10 GND? GND?
11 GND GND (USB black1, black2, shield) Motherboard USB Header - Pin 8
12 USB2 -  (USB white2) Motherboard USB Header - Pin 4
13 USB2 +  (USB green2) Motherboard USB Header - Pin 6
14 GND GND (USB black1, black2, shield)
15 VCC +5v  FNT 2, FNT 3 (USB red1, red2)
16 GND GND (USB black1, black2, shield)
17 USB1 - (USB white1) Motherboard USB Header - Pin 3
18 USB1 + (USB green1)  Motherboard USB Header - Pin 5
19 GND GND (USB black1, black2, shield)
20 PWR SWITCH LEFT SIDE (Both) CTRL 2
21 Pin removed —
22 HDD LED NEG CTRL 4
23 PWR LED GREEN POS CTRL 5
24 ESUP LED NEG CTRL 13
25 GND GND (USB black1, black2, shield)
26 ?  
27 PWR LED YELLOW POS CTRL 9
28 ESUP SWITCH RIGHT SIDE (Both) CTRL 8
29 GND GND (USB black1, black2, shield) S-GND: Motherboard USB Header - Pin 10
30 INTRUDER 1 INTRUDER 1
31 EXT_SPK 2 EXT_SPK 2
32 INTRUDER 3 INTRUDER 3
33 EXT_SPK 4 EXT_SPK 4
34 EXT_SPK 1 EXT_SPK 1


Motherboard USB Header Pinout (http://www.frontx.com/cpx108_2.html)


Wiring Diagram for USB