The Dell Dimension 2350 and 2400 desktop computers use a proprietary 20-position front-panel header (designated J16 on the motherboard) to carry two USB 2.0 ports and a stereo headphone jack. Dell never published a motherboard-level pinout diagram for J16 in any public service manual. The connector accommodates 14 active pins plus one key position (pin 16); USB signal levels follow the USB 2.0 Specification (USB Implementers Forum, April 2000). The audio jack is wired as an AC97 headphone output and, unlike the Dimension 3000 variant, does not mute the rear speakers when headphones are inserted.
| Name | Pin | Description |
|---|---|---|
| Data0- | 1 | Data - for USB port 0 (Bottom) |
| Data0+ | 3 | Data + for USB port 0 (Bottom) |
| Data1- | 5 | Data - for USB port 1 (top) |
| Data1+ | 7 | Data + for USB port 1 (top) |
| GND | 9 | Ground |
| GND | 11 | Ground |
| ? | 13 | Unknown |
| ? | 15 | Unknown |
| GND | 17 | Ground |
| ? | 19 | Unkonwn |
| ? | 2 | Unkonwn |
| Vcc | 4 | +5V for USB |
| ? | 6 | Unkonwn |
| Vcc | 8 | +5V for USB |
| Ring | 10 | Speaker Ring & RS Terminal |
| Tip | 12 | Speaker Tip & TS Terminal |
| ? | 14 | Unknown |
| Keyed | 16 | |
| GND | 18 | Ground |
| ? | 20 | Unknown |
Signals
- Data0− — D− differential data line for USB port 0 (bottom front-panel port)
- Data0+ — D+ differential data line for USB port 0 (bottom front-panel port)
- Data1− — D− differential data line for USB port 1 (top front-panel port)
- Data1+ — D+ differential data line for USB port 1 (top front-panel port)
- Vcc — +5 V bus power (VBUS) supplying both USB ports
- GND — signal and power ground common to USB and audio circuits
- Ring — headphone jack ring contact (right audio channel return / RS terminal)
- Tip — headphone jack tip contact (speaker tip / TS terminal)
- Keyed — pin 16 is a key position (no pin present); prevents incorrect cable insertion
- Pins 2, 6, 13, 14, 15, 19, 20 — function not publicly documented
Notes
- The Dimension 2350 and 2400 share an identical J16 front-panel connector and cable (J24 proprietary ribbon); parts are interchangeable between the two models.
- Pin 16 is physically absent (key); the mating cable is keyed to prevent reversed insertion.
- The audio output is AC97-compliant but does not assert the mute-rear signal when headphones are plugged in — rear speaker output continues uninterrupted, unlike the Dimension 3000.
- USB D+ and D− lines carry High-Speed (480 Mbit/s) or Full-Speed (12 Mbit/s) differential signals per USB 2.0; keep traces short and matched-length on any adapter cable.
References
- Universal Serial Bus Specification, Revision 2.0 — USB Implementers Forum, April 2000