UL 924-2020 pdf download – Emergency Lighting and Power Equipment.
4.33 LAMPHEAD – As applicable to unit equipment, a lamp assembly mounted externally to the main enclosure of the equipment with a swivel or equivalent mounting means so as to be adjustable. 4.34 LEGEND – Text (in English or other languages as appropriate for the installation site) or graphical symbols intended to transmit a specific message associated with life safety, in accordance with an adopted building or fire code. 4.35 LIMITING IMPEDANCE CIRCUIT – A circuit supplied by an impedance that, under any load condition including when a direct short is applied across the source output: a) Has a calculated power dissipation of 15 W or less, and b) Does not incur any opened or shorted components. The limiting impedance shall additionally function under any single fault condition unless it consists of a single resistor, or of a single capacitor that complies with the Standard for Fixed Capacitors for Use in Electronic Equipment – Part 14: Sectional Specification: Fixed Capacitors for Electromagnetic Interference Suppression and Connection to the Supply Mains, UL 60384-14. See Determination of Limiting Impedance Circuit Status, Section 51. 4.36 LOW-FREQUENCY INVERTER – An arrangement of solid-state circuitry designed to convert direct-current power to low-frequency (50 – 800 hertz), alternating current and the voltage required to operate lighting and power equipment. 4.37 LOW-VOLTAGE, LIMITED-ENERGY CIRCUIT – A circuit supplied by a source of open circuit potential below the risk of electric shock and maximum 8 A, or 150/V amps for circuits operating between 30 – 60 Vdc, i measured after one minute of operation. See Section 50. 4.38 LUMINANCE – The amount of light emitted from a surface, measured in foot-lamberts or candelas per square meter. 4.39 MULTI-CIRCUIT DISTRIBUTION EQUIPMENT – Any multi-circuit distribution panel incorporating individual branch circuit overcurrent protection.
4.52 SELF-LUMINOUS EXIT SIGN – A sign with an integral legend that is powered continuously by a self-contained energy source other than a battery, such as radioactive tritium gas. Operation of a self- luminous exit sign is independent of external power supplies or other external forms of energy. This definition does not include exit signs dependent upon photoluminescent materials. 4.53 SERVICE – Tasks intended to be performed on-site by qualified personnel and that requires either a tool to access any compartment or specialized knowledge for performance of the task. 4.54 TRANSLUCENT – The property of letting light through without being transparent. As applicable to exit signs, a luminous surface that is not transparent, but provides the same effect as a translucent material that is illuminated from the back is also considered to be translucent. For example, a composite construction consisting of a transparent material applied over a luminous non-transparent surface as in edge-lighted exit sign constructions is considered to be translucent. 4.55 UNFILTERED – In the context of a luminaire intended to activate a photoluminescent exit sign, the lack of a lens or diffuser that removes any appreciable portion of the UV spectrum. 4.56 UNIT EQUIPMENT – A complete, enclosed unit assembly, consisting of a rechargeable battery, a battery charging means, provisions for one or more lamps either mounted on the equipment or remote or both, and an ELCD (or ELCF circuit) to energize the lamps automatically upon failure of the normal supply. Terminals or leads are provided for the connection of remote lamps. 4.57 VENTED BATTERY/CELL – A battery/cell provided with positive openings that permit free interchange of cell gases with the outside atmosphere. 4.58 VISIBLE – Legible (as pertains to text) and distinguishable from other text or symbols.