These requirements cover construction@ performance@ and maintenance of police station connected burglar-alarm units and systems for use in mercantile premises@ mercantile safes and vaults@ and bank safes and vaults. As covered by these requirements@ a police station connected alarm system consists of protective circuits and devices@ connected through control apparatus to an enclosed tamper-protected sounding device mounted on an outside or inside wall of the building in which the protected property is situated@ and a constantly-manned police department (see 1.8 and 52.1). Intrusion into or disturbance of the units or wiring causes the sounding device to be actuated and a signal to be transmitted to the police department. The sounding device and signal to the police department continue to operate until it is stopped by using the proper control key@ by exhaustion of the power supply@ or by action of an automatic timing element that is preset for a definite operating period. These systems usually 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 operation of a police station connected alarm system is partially under the control and domination of the owner or others interested in the property. However@ it is required that police station connected systems be maintained under the care and regular inspection service of the installing company. The installing company is expected to respond promptly to troubles or calls for service on report of the owner or police department. See Mercantile Premises Alarm Systems@ Maintenance@ Section 65 and Bank Safe and Vault Alarm Systems@ Maintenance@ Section 75. It is the responsibility of the owner to switch the system on and off duty and to report malfunctioning of the system to the service company. Police station connected mercantile burglar-alarm systems transmission means may be designated as standard line security or encrypted line security and are designated as to their acceptability for use either on mercantile premises or on mercantile safes and vaults. See Standard Line Security Equipment@ Section 59@ and Encrypted Line Security Equipment@ Section 59A. Police station connected bank burglar-alarm systems transmission means may be designated as standard line security or encrypted line security and are for use on bank safes and vaults. See Standard Line Security Equipment@ Section 59@ and Encrypted Line Security Equipment@ Section 59A. Equipment intended for combination burglar-alarm and fire-protective signaling systems is also expected to comply@ with the Standard for Control Units for Fire-Protective Signaling Systems@ UL 864. Devices installed on individual properties are further classified as to extent of protection at each location. Rules covering installation and classification (of extent) of alarm equipment at individual locations are published in the Standard for Installation and Classification of Burglar and Holdup Alarm Systems@ UL 681@ which should be consulted by burglar-alarm installers. The connection to a police department may be: a) Direct or b) Through a central station or a residential monitoring station complying with the Standard for Central-Station Alarm Services@ UL 827. Deleted August 31@ 2001