Epson 503c - Manual (Page 100)

94 Appendix C: Technical Specifications
Computer Video Port Pin Assignments
The Computer port is a female video RGB, 15-pin micro-D-style
connector. Here are its pin assignments:
Pin no. Computer port
1 Red video
2 Green video
3 Blue video
4 GND
5 GND
6 Red GND
7 Green GND
8 Blue GND
9 Reserved
10 Synchronous GND
11 GND
12 SDA
13 Horizontal sync / composite sync
14 Vertical sync
15 SCL