STX 165 :: What are the STX 165 and STX 165R power requirements? Jul 23, 2014 | What are the STX 165 and STX 165R power requirements? 1 Comment admin on July 23, 2014 at 6:30 pm Both the STX 165 and STX 165R (Remote) are designed to operate from 11-33Vdc. Current consumption is dependent on three factors: 1) Squawk Code. The higher the squawk code the more pulses that are transmitted. More pulses require more current. 2) PRF (Pulse Repetition Rate). Like the squawk code, the higher the PRF rate the more current a transponder will draw. 3) In the case of the STX 165 that has a built-in encoder current increase when the encoder heater is on.