Mystim Sultry Sub Channel Setting

Sigh, I ordered 3 extra Sultry Sub units to go with the Cluster Buster and failed to notice that the vendor only offered channel 2. The parts have not arrived yet (damn pandemic), but I expect to end up with 3 remote units all listening to channel 2 :unamused:

Does anyone know if the channels are selectable? Perhaps a user accessible dipswich?

Grr, I was so looking forward to having 4 channels and now it looks like I will only have 2. :sleepy: