FUTABA 3GR-2.4G Instruction Manual page 20

Receiver
Connectors
3: CH3 servo (CH3)
2: Throttle servo (CH2)
1: Steering servo (CH1)
B/C: Power connector/DSC connector
RS232C: (for factory use only)
Antenna
Coaxial cable
R603FF
receiver
For the receiver, servos, and other connections, see page 21.
20