Overview
The Allen-Bradley 855T-B24DD4 is a compact 70mm stack light module designed for industrial signaling and machine status indication. This integrated 2-circuit light/sound module combines a red incandescent lens with a piezo sounder in a single stackable unit, eliminating the need for separate sound devices. Rated for 24V AC/DC operation, it delivers steady illumination and audible signaling for production floor visibility and operator awareness.
Key Features
- Integrated 2-circuit light and sound module in single 70mm housing
- Piezo sounder with DIP switch selectable pulsing or continuous mode
- Red incandescent lens for clear visual indication
- Stackable design—compatible with up to three light modules maximum per stack
- Absorbs up to 3 mA leakage current from solid-state PLC outputs
- Certifications: CUL, CE, KC, UL
Technical Specifications
- Voltage Rating: 24V AC/DC
- Lamp Type: Incandescent
- Lens Color: Red
- Housing Color: Black
- Operation Type: 2-Circuit Steady (light and sound independent)
- Sound Module: Piezo with DIP switch pulsing/continuous selection
- Module Diameter: 70mm
- Compatible Bases: 855T-BSB, 855T-BCB (stack), or 855T-BPM10/25/40 (pole mount)
- Certifications: CUL, CE, KC, UL
- Weight: 0.33 lb (0.15 kg)
Typical Applications
- Machine running/ready state indication
- Fault and warning condition alarms on production equipment
- Assembly line status signaling in manufacturing facilities
- Equipment maintenance and emergency stop alerts
- Industrial process control visual-audible feedback systems
Compatibility & Replacements
The 855T-B24DD4 is part of the Allen-Bradley 855T Control Tower stack light family and integrates with standard 855T bases (BSB, BCB) and pole-mount adapters (BPM10, BPM25, BPM40). The two-circuit design allows the light and sound to be controlled independently from separate PLC outputs or relay circuits, providing flexible signaling configuration. Related 855T modules in red include the 855T-B24DN4 (light-only) and 855T-B24DD5, DD6, DD7, DD8 (alternative color versions). Note: This product was discontinued by the manufacturer on October 1, 2019; it remains available as surplus stock from authorized distributors.
