The Mitsubishi QX42 is a 64-point sink-type DC input module for the Melsec Q Series PLC platform. Each input draws 4 mA at 24 VDC, with photocoupler isolation between field and logic. Internal consumption from the backplane is 90 mA. This module handles 64 discrete DC inputs in a single slot, making it a high-density choice for monitoring limit switches, proximity sensors, or pushbutton arrays on a single backplane address.
The 64-point count means this module occupies 64 I/O points on the Q Series backplane. The 4 mA per input is typical for sink DC modules; it keeps the loop draw low enough that a standard 24 VDC power supply can feed a full rack without excessive current demand. Photocoupler isolation provides basic galvanic separation between the field wiring and the PLC logic — adequate for industrial control panels where common-mode voltages stay within the isolation rating.