B401/W

The NOTIFIER B401/W is the white version of the B401 standard plug-in detector base, designed for 2-wire conventional smoke detectors like the 2151, SD651, or System Sensor S300 series in fire alarm systems.
It provides screw terminals for power (+/-), remote annunciator/LED connections, and a built-in EOL resistor jumper, with a theft-resistant latch and low-profile 4-inch diameter for aesthetic installations.
Key Specifications
Feature
Specification
Type
2-wire detector base (no electronics); white finish 
Compatibility
2151/SD651 photo smoke; heat detectors; remote LED 
Dimensions
4.1″ diameter × 2.0″ height (10.4 × 5.1 cm); 5.2 oz 
Mounting
4″ square/round boxes; 50/60 mm European boxes 
Wiring
Screw terminals; EOL jumper for continuity 
Environment
32–120°F (0–49°C); 10–93% RH; UL/CSFM listed