These requirements cover electrically and electronically operated bells@ buzzers@ horns@ and similar audible signal appliances@ rated 300 volts or less@ for general or fire-protective signaling service and intended for indoor or outdoor locations or both in accordance with the National Electrical Code@ NFPA 70@ and the National Fire Alarm Code@ NFPA 72. These requirements cover audible signal appliances for use in ordinary locations. Audible signal appliances for use in hazardous locations@ as defined in the National Electrical Code@ NFPA 70@ are judged on the basis of their compliance with these requirements and further appropriate examination and tests to determine if they are acceptable for such use. These requirements do not cover door bells@ buzzers@ and chimes used in household and similar applications and intended for operation on Class 2 signal circuits as defined in the National Electrical Code@ NFPA 70. A supplementary visual signal@ incorporated as part of an audible signal appliance which is intended for fire alarm application@ is covered by the applicable requirements in this standard@ and in the Standard for Visual Signaling Appliances ?C Private Mode Emergency and General Utility Signaling@ UL 1638@ or in the Standard for Signaling Devices for the Hearing Impaired@ UL 1971. A supplementary visual signal@ incorporated as part of an audible signal appliance which is intended for general signaling (nonfire alarm service)@ is covered by the applicable requirements of this standard.