Allen-Bradley 1771-IV DC Driver Logic Input Module

Allen-Bradley 1771-IV is an 8-point DC driver logic input module designed for PLC‑5 I/O racks, converting 12–24 V DC field signals into logic‑level inputs for the controller. Each of its eight inputs is specified for a 12–24 V DC range and typically draws about 8 mA at 12 V (24 mA at 24 V), with an input impedance that ranges from roughly 1–2 kΩ in the on state to 2–3 kΩ in the off state. The module dissipates up to about 5.8 W of power and exhibits propagation delays of roughly 15 ms (low‑to‑high, +7 ms) and 15 ms (high‑to‑low, +7 ms) for input transitions, fitting into a PLC‑5 I/O chassis as an eight‑input digital DC input card. Note that Rockwell Automation discontinued the 1771‑IV as of March 31, 2021, reflecting its status as a legacy AB module, commonly used to monitor digital signals from sensors and switches in industrial control panels.