The Patton EPG Model 509 is available in two versions: the 509/6 for protection of RS-422 equipment, and the 509/25 for protection of EIA-574 (RS-232) equipment. Both versions guard all 9 pins on the DB-9 interface and divert surge energy to their male and female D-shells.

- Model 509/6: 7.5V Clamping Voltage (RS-422)
- Model 509/25: 28V Clamping Voltage (RS-232)
- Combined Surge Handling of 5400 Watts
- Shipped with mounting hardware pre-installed.