EPSON PHOTO PC 500 DIGITAL CAMERA

Serial meaning 2.5mm stereo headphone looking jack to DB9 or "atari joystick" looking plug? I had one on my first Toshiba PDR-M1 camera but that was like 9 years ago. You can probably find the pinouts online for that cable, I believe it is a standardized cable.

The stereo plug is wired to the PC serial port as shown in the following diagram:
tip ring sleeve +---------------------------------+
| |
/-------+-----+--------------+ |
| RxD | Gnd | TxD | 2.5 mm Stero Plug |
\-------+-----+--------------+ |
| |
DB9*: pin 2 pin 5 pin 3 +---------------------------------+

DB9*: Optionally short together pin 4 (DTR) to pin 6 (DSR) and
pin 7 (RTS) to pin 8 (CTS)
The following table also describes the camera cable's wiring: Camera PC's
Plug DB9* Signal Name Direction
---- ---- ----------- ---------
- 1 Carrier detect (CD) input to PC
tip 2 Receive data (RxD) input to PC
sleeve 3 Transmit data (TxD) output from PC
- 4 \ Data terminal ready (DTR) output from PC
ring 5 | Signal ground (Gnd) -
- 6 / Data set ready (DSR) input to PC
- 7 \ Request to send (RTS) output from PC
- 8 / Clear to send (CTS) input to PC
- 9 Ring indicator (RI) input to PC
* Note that the cable's D-subminature DB9 RS-232 serial port connector is female. This connector also goes by the historically more correct name of "DE-9J".