Allen-Bradley 1771-IQ16 Isolated DC Input Module

The Allen-Bradley 1771-IQ16 is a 16-point isolated DC input module for the PLC-5 system that converts field 24V DC signals into discrete inputs for the controller while providing galvanic isolation between the inputs and the backplane. This 16-channel module is designed specifically for 24V DC operation within the 1771 PLC-5 family, enabling expansion of digital inputs in PLC-5 installations. It accepts a 10–32V DC input range and draws about 100 mA of backplane current, with isolation levels that meet UL 508 and CSA C22.2 standards to help protect the controller from field wiring faults. The 1771-IQ16 is not compatible with the 1771-AL local I/O adapter, so it must be used with the proper PLC-5 backplane and rack configuration. Typical applications include sensing 16 independent sensors or switches in factory automation, process monitoring, and safety interlock circuits where isolated inputs improve fault isolation and reliability.