The proprietary round 10-pin connector used by the pro cameras has the following signals (pin numbers run from 11 o'clock position to 1 o'clock position, i.e. counterclockwise from top left):
- Pin 1 — Data Receive
- Pin 2 — Battery Voltage
- Pin 3 — +5V regulated, Meter On Trigger
- Pin 4 — Shutter Release (full shutter release)
- Pin 5 — Data Send
- Pin 6 — Signal Ground
- Pin 7 — Power Ground
- Pin 8 — Shutter Release Relay (to next camera)
- Pin 9 — Camera Activate (half shutter release)
- Pin 10 — Not connected
These connectors are found on the D200, D300, D300s, D700, D800, D800E, D810, D3, D3s, D3x, D4, and D4s, as well as the Fujfilm S3 Pro and S5 Pro.
This information is not verified, nor it it certified by Nikon. Use at your own risk.