Modem-M64 offers point to point communication to communicate between 2 modems. There are several parallel channels available, and it is possible to switch channels in use which allows communication between more than 2 modems, but not at the same time.

Modem A and B is configured to use channel 2
Modem C is configured to use channel 3

Modem A can now can communicate with Modem B (but not modem C).
If modem A now changes channel to channel 3 it can communicate with modem C (but not modem B).