These requirements apply to the construction@ performance and operation of equipment intended for use in proprietary burglar alarm units and systems used to protect against burglary. These products are normally intended for indoor use. A proprietary burglar alarm system as referred to by these requirements is a system in which alarm initiating circuits and devices are installed at a property and are connected directly or indirectly to constantly monitored receiving equipment at a central supervising station. The central supervising station is located at the protected property and intended for operation by personnel responsible to the owner of the protected property. The protected property may consist of a single property or of noncontiguous properties under a single ownership. The system is arranged so that a predetermined change in the alarm initiating circuits or devices automatically causes transmission of an alarm signal over a supervised signaling channel to the central supervising station. These systems normally operate within the limits of Class 2 remote-control and signal circuits as defined by Article 725 of the National Electrical Code@ NFPA 70. The protection circuit must respond to both an increase and a decrease in the circuit resistance or current within the limits indicated in the appropriate sections of this standard. See 53.3@ 57.2@ and 61.6. Revised 1.4 effective March 21@ 2007 A system that provides line security may be classified as either standard line security or encrypted line security. See Standard Line Security Equipment@ Section 64@ and Encrypted Line Security Equipment@ Section 64A. Revised 1.5 effective March 21@ 2007 Protective devices installed on individual properties are further classified as to extent of protection at each location. Requirements covering installation and classification (of extent) of alarm protective equipment at individual locations are published in the Standard for Installation and Classification of Burglar and Holdup Alarm Systems@ UL 681@ which is intended to be referenced by burglar-alarm installers. Revised 1.6 effective March 21@ 2007 Proprietary burglar alarm units and systems are also specially designated as to their intended use on mercantile premises@ mercantile safes and vaults@ and bank safes and vaults. Equipment intended for combination burglar alarm and fire-protective signaling systems shall comply with the requirements in the Standard for Control Units for Fire-Protective Signaling Systems@ UL 864. A product that contains features@ characteristics@ components@ materials@ or systems new or different from those covered by the requirements in this Standard@ and that involves a risk of fire@ electric shock@ or injury to persons shall be evaluated using the appropriate additional component and end-product requirements to determine that the level of safety as originally anticipated by the intent of this Standard is maintained. A product whose features@ characteristics@ components@ materials@ or systems conflict with specific requirements or provisions of this Standard shall not be judged to comply with this Standard. Where appropriate@ revision of requirements shall be proposed and adopted in conformance with the methods employed for development@ revision@ and implementation of this Standard. 1.9 revised February 1@ 1999