Frsky R-XSR receivers are now coming installed with ACCESS firmware. To bind with ACCST only radios, a firmware update is required. Firmware can be found here: https://www.frsky-rc.com/r-xsr/ (Select history firmware download for ACCST 1.0 firmware)
The FrSky ultra mini receiver R-XSR is the evolution of the popular full range XSR receiver. The R-XSR is a standalone receiver with all the functionality of the full size XSR (including telemetry), but at 1/3 size and weight of XSR receiver. The R-XSR also has an integrated diversity with 2x antennas for a solid RC link, and the IPEX connector makes it convenient to replace antennas.
Ultra mini size and light weight
Support telemetry and Smart Port enabled
Switchable SBUS/ CPPM signal output
Supports redundancy function
IPEX connector, replaceable antennas
Dimension: 16*11*5.4mm (L*W*H)
Number of channels: 16CH (1-16CH from SBUS channel, 1~8CH from CPPM channel)
Operating Voltage Range: 4~10V
Compatibility: FrSky X Series modules and radios in D16 mode
Download the R-XSR Manual here.