Allen-Bradley 1746-IA4 Digital AC Input Module

The Allen‑Bradley 1746-IA4 Digital AC Input Module is a four‑channel input block for SLC 500 controllers that converts AC signal presence into discrete PLC inputs. It accepts 85–132 VAC signals at a nominal 47–63 Hz, designed for general‑purpose 120 VAC sensing in industrial panels, and it draws backplane current from the 5 V rail of the processor backplane (approximately 35 mA). Each of the four channels provides a digital input, with a delayed response designed to accommodate typical AC signal sources in automation environments. The module specifies an on‑delay of up to 35 ms and an off‑delay of up to 45 ms, with an off‑state current of no more than 2 mA, ensuring clean transitions for noisy line conditions. When deployed in an SLC 500 I/O chassis, the IA4 integrates directly with other 1746 family modules to extend a controller’s input capability without requiring external conversion hardware. Typical applications include monitoring relays, contactors, sensors, and other 120 VAC devices within manual and automated control circuits, enabling straightforward visibility of field signals to the PLC without external conditioning. This module is a compact, four‑channel solution designed specifically for legacy Allen‑Bradley automation architectures, supporting the broader 1746 I/O lineup and the established SLC 500 backplane ecosystem.