This is the Futaba R304SB-E T-FHSS 4-Channel Telemetry 2.4GHz Receiver for Electric Only.
Features:
Power Requirement Rated Voltage: 4.8-7.4V
Usable Voltage: 3.5-8.4V
System: T-FHSS (auto detection) w/ SBUS2 port
Specifications:
Futaba System: T-FHSS
S.Bus2: Yes
Channels: 4
Size: 35.1x23.2x12.5mm
Weight: 7g
Rated Voltage: 4.8-7.4V
Operating Voltage: 3.5-8.4V