American National Standard for Electric Lamps--Dimensions for Projection Lamps--Double-Contact, Medium Ring (Special B), Base-up Type
美国电灯国家标准投影灯尺寸底座式双触点中环(特殊B型)
ANSI C78.1401-2004 (R2009, R2016) establishes the dimensions essential to the interchangeability of lamps of the double-contact, medium ring (Special B), base-up type. It is not intended to prescribe either operating characteristics or details of design, such as the shape of the ventilation ports or the method of attachment of the prefocus ring to the base.