Futaba R2104GF 4-Channel 2.4GHz S-FHSS Receiver 4PL Futaba S-FHSS/FHSS 4-Channel Receiver.
Click photo to enlarge.
Futaba R2104GF 4-Channel 2.4GHz S-FHSS Receiver 4PL Part# 0-FUTL7616
Power requirement: 4.8V or 6V NiCd battery Receiving frequency: 2.4GHz band System: S-FHSS/FHSS system (auto detection) Dimensions: 1.54 x 1.02 x 0.39 in (39 x 26 x 10 mm)