Wireless
If you see RECEIVE CHANNEL or SEND CHANNEL in the mapper of a unit, it means that the unit support wireless feature.

note
Most blocks need to be set as off-board to enable the feature
The SEND CHANNEL can be considered as a virtual output port.
The RECEIVE CHANNEL can be considered as a virtual input port.
If unit A's SEND CHANNEL is same as unit B's RECEIVE CHANNEL, you can imagine that A's output port is connected to B's input port.
warning
Similar with ordinary ports, it is not recommend to share the same SEND CHANNEL amoung different units (equivalent to connecting an input port with multiple output ports).