This is a DC Power Supply and Fan Module for the Cisco ME 3400E-24TS-M and the Cisco ME 3400EG-12CS-M switches (available separately). Your switch ships with at least one power-supply module installed, and the power-supply module is a field-replaceable unit (FRU). The DC-power-supply module has dual input feeds (A and B) and supports input voltages between -36 to -72 VDC for telecom applications and +18 to +36 VDC for industrial applications.The DC-power-supply module ships with a terminal block to be wired for DC-power outlet connections. Each power supply is cooled by internal fans. For maximum efficiency, at least two of the four fans should be operational in a warm environment. A fan failure triggers an alarm. When a fan fails, replace the power supply immediately.