Direct answer: Both are slide-gate operators with a current published limit of 27 feet and 600 pounds. The big difference is power.
FR is the AC model
The Eagle 1000 FR uses a 115 VAC motor. Battery backup is optional, and the FR foot pedal lets you release the gate during an outage.
DC is the solar-ready model
The Eagle 1000 DC uses a 24 VDC motor, has built-in battery backup, and can run from 120/220 VAC or a 24 V solar setup.