An alarm monitoring center, central monitoring station (also known as "CMS" or wholesale central station), or alarm receiving center (also known as ARC) is a company that provides services to monitor burglar, fire and residential alarm systems. The Central Monitoring Station may also provide watchman and supervisory services. "It functions as a support system for critical event management devices, such as: security alarm panels, gas and temperature gauges, PERS devices, crash detection devices, integrated video systems, and even mobile applications." When a genuine alert is confirmed, the monitoring team may immediately contact the relevant emergency service. Central monitoring stations use special telephone and mobile lines, radio channels, computers, software and trained staff to monitor their customers' security systems and call the appropriate authorities in the event an alarm signal is received. Typically, there is a monthly fee for services rendered. Because quality and experience can vary greatly among alarm companies, prospective customers are well advised to do their own research before making a final choice. Not all alarm companies monitor the systems they install and may outsource these services to another company. Some facilities are certified by independent agencies. In the USA, Underwriters Laboratories (UL) is a leader in inspection and certification of central-stations. UL Standard 827 must be adhered to in order to maintain a UL issued central-station listing. UL conducts annual audits of these listed facilities to ensure compliance. "UL listed" companies typically offer higher levels of service and reliability because they are mandated to follow certain regulations. Higher levels of service also include range of services, and a separation from companies with conflicts of interest who may be owned or operated by entities that in fact compete with the central station's customers. If the UL listed central station is "automated", the computers and software must meet special requirements, processing and storing very large amounts of data and integration with many different alarm protocols. In addition, many central monitoring stations seek to become FM approved in order to demonstrate additional levels of regulation compliance and interest for customer safety. Incoming signals are processed by digital alarm receivers; these convert the incoming event packets to serial or TCP packets which are then analysed by the Central Station software. Event packets can be communicated over any transmission medium: PSTN, GSM, radio, direct line, Ethernet, GPRS, etc. Central Station Services An Alarm Monitoring Center can offer a handful of services, but