521-0387 is a T-1 3/4 midget flange base incandescent lamp designed for low-voltage indicator and illumination applications. The lamp operates at 28.0V with a current draw of 0.04A, delivering a luminous intensity of 0.30 MSCD (mean spherical candlepower) and consuming approximately 1.12W of power. With a rated lifespan of 7,000 hours, this lamp provides reliable long-term operation in demanding environments. It is commonly used in aircraft instrumentation panels, military equipment, telecommunications systems, and other applications requiring compact, durable indicator lighting with consistent brightness output.