The legacy bulk AC to 24 VDC power supply provides power to field devices and System Power Supplies (Dual DC/DC). In general, AI cards, AO cards, and dry contact DI cards use small amounts of current. Thus, the legacy bulk AC to 24 VDC power supply provides enough power for approximately 40 of these types of I/O cards.
If you are supplying power to DO cards with high side switches, you must evaluate the power requirements carefully. Refer to the manufacturer’s specifications for your field devices to determine the load.