DC 48v alarm management system which controls fans, air conditions, ligt etc?

Question

The AC power is terminated on the printed circuit boardof the alarm management unit.

what is the advantage and disadvantages of a DC operated unit controlling AC unit on the same printed circuit board.

If the DC section of the alarm unit have a separate printed circuit board and the electrical appliance with 240v supply also have a separate printed circuit board, but is being control by a signal cable from the DC printed circuit board, what will be the advantage and disadvantages

Answer 1

Use a small amount of energy to control a large amount of energy.

: )