For listing purposes, Tables 12(A) and 12(B) provide the required power source limitations for power-limited fire alarm sources. Table 12(A) applies for alternating current sources, and Table 12(B) applies for direct current sources.
The power for power-limited fire alarm circuits shall be either (1) inherently limited requiring no overcurrent protection, or (2) not inherently limited requiring the power to be limited by a combination of power source and overcurrent protection.
As part of the listing, the PLFA power source shall be durably marked where plainly visible to indicate that it is a power-limited fire alarm power source.
The overcurrent device, where required, shall be located at the point where the conductor to be protected receives its supply and shall not be interchangeable with devices of higher ratings. The overcurrent device shall be permitted as an integral part of the power source.