M2M (Modem-to-Modem) on Sega Saturn refers to the original direct multiplayer connection system using Net Link modems, where two Saturn consoles link up peer-to-peer over phone lines without central servers.
Players insert a Net Link modem cartridge into each Saturn's top slot, connect the modems via RJ11 telephone cable (simulating a phone line), and dial each other directly using in-game Net Link menus.
Games like Sega Rally Championship, Saturn Bomberman, and Blast Wind supported this for head-to-head play at 28.8kbps speeds. No internet required — pure analog dial-up emulation.
The cable must be LVI (Line Voltage Inducer) type because Saturn Net Link modems expect real phone line voltage (+48V DC ring signal) to trigger the dial tone and handshake process.
Supported games require Net Link patches that modify the ROM to recognize modem dialing and synchronize versions between players. Mismatched versions will cause connection failures.