One transmitter.
You can bind as many receivers as you like to a transmitter, but they would all respond if turned on.
The loco selection feature allows 12 (or more, see above) to be controlled.
If you want to 'consist' two or more loco's, you would bind them to the same transmitter and loco selection position. As with DCC, the performance of the loco's would need to be similar.
As an example:
You could set the loco bound to selection position '1' running around the garden. Change to another selection position, and that first loco continues running. You can then control the loco you have changed the selection too.
PhilP.