Refers to the number of devices that you can connect into a receiver and control; also references the frequency a transmitter broadcast on.
Utilizing the SRXL protocol, receivers with SRXL can utilize X-Plus to expand the number of allowed channel outputs with a X-Plus Expansion Module. These additional X-Plus Channels communicate at a slower rate and resolution (512ms compared to 1024ms) and are intended for non-control surface functions such as bomb drops, lights, winches, and retractable landing gear.