The MMF-300 Monitor Module is intended for use in addressable, two-wire systems, where the individual address of each module is se- lected using the built-in rotary switches. It provides either a 2-wire or 4-wire fault tolerant Initiating Device Circuit (IDC) for normally open contact fire alarm or supervisory devices. The module has a panel controlled LED indicator. The MMF-300 can be used to replace an M300 module in existing systems.