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The Patton EPG Model 503S universal surge protector guards any RS-232 system (synchronous or asynchronous) against data loss and hardware damage due to data line transients. There are many data line surge generators: lightning strikes, fluorescent lights, elevator motors, even UPSs. AC protection alone is not enough! The Model 503S diverts harmful data line surges to chassis ground (through either D-shell) before they reach your hardware.