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Transmitting Fire Alarms Reliably After the Sunset of the PSTN

Transmitting Fire Alarms Reliably After the Sunset of the PSTN. Gregory Lapin, PhD, PE King-Fisher Company, inc Lowell, MA. Topics. What is the PSTN? Digital Dialers What is happening to the PSTN? NFPA Requirements How will fire alarms cope?. What is the PSTN?.

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Transmitting Fire Alarms Reliably After the Sunset of the PSTN

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  1. Transmitting Fire Alarms Reliably After theSunset of the PSTN Gregory Lapin, PhD, PE King-Fisher Company, inc Lowell, MA

  2. Topics • What is the PSTN? • Digital Dialers • What is happening to the PSTN? • NFPA Requirements • How will fire alarms cope? King-Fisher Company, inc

  3. What is the PSTN? • Public Switched Telephone Network • A regulated monopoly. • Governed by FCC and state regulations. • 100-years old. • Almost all forms of telephone communication rely on the PSTN to some extent. • Available anywhere in the USA at a reasonable price. King-Fisher Company, inc

  4. Features of the PSTN • Highly reliable (Four 9’s = 99.99% availability) • How many times have you lost power at home but your old landline telephone still worked? • Dedicated hardware • Every telephone line has its own pair of wires connecting you to the Central Office. • When calls are combined in “trunks” your call has time slots reserved for your voice only. • Line powered • Backup power available for at least 24 hours. • Often good for a week or more. • Power is delivered directly to the end-of-line devices. King-Fisher Company, inc

  5. Backup Power in the Central Office King-Fisher Company, inc

  6. PSTN Quality • Voice bandwidth consistent. • 300-3400 Hz ; not Hi-Fi but understandable. • Low Latency • Less than 100 msec, usually < 40 msec. • No voice drop outs. • Standard CODECs (A-Law and μ-Law). • Time to Dial Tone (< 0.5 sec). • Time to Disconnect (< 2 sec). King-Fisher Company, inc

  7. Regulated Monopoly • The PSTN has been the telephone system in the US for 100 years. • Prices are fixed by the state commerce commissions. • PSTN is available anywhere in the USA. • Subsidized by USF for rural and low income • Independent competition to the PSTN was first allowed in 1984. King-Fisher Company, inc

  8. Regulated Monopoly • PSTN must meet operating standards specified in FCC rules. • PSTN is used/required for use in many parts of the overall communications landscape: • PSAPs (911) only connected via PSTN. • PSTN provides the link between many different telecommunications vendors. King-Fisher Company, inc

  9. Digital Dialers • The most common method of reporting fire alarms to the emergency dispatch. • There are about 40 million digital dialers in use in the United States; many are used to report fire alarms. • Also known as DACTs. King-Fisher Company, inc

  10. Digital Dialers • Modem devices that send alarms by telephone. • Designed around the characteristics of the PSTN. • Convert digital data to tones. • Depend on precise timing of signals. • Depend on continuity of communications. King-Fisher Company, inc

  11. Digital Dialers • Digital dialers fail when: • There is insufficient voice bandwidth. • There are dropouts in the audio transmission. • There are excessive delays in transmission. • CODEC does not match standards. • There is too much voice compression. King-Fisher Company, inc

  12. Digital Dialers • Do not work well over cellular networks. • Can be unreliable on VOIP networks. • Central Station Alarm Association warns against VOIP connections. • Must be used on networks with at least 24 hours of backup power. King-Fisher Company, inc

  13. What is Replacing PSTN? • Cellular Telephones. • Voice Over IP (VOIP). • Skype. • MagicJack. • Cable TV Telephone Service. • e.g. Comcast Xfinity, Cox. • Fiber Optic Telecommunications Service. • e.g. Verizon FIOS, ATT Uverse. King-Fisher Company, inc

  14. Cord cutting, especially younger segments Source: National Center for Health Statistics As of May 2010, 23% of respondents in a study lived in a mobile-only household. The same study also found that 37% of adults in the 18-24 and 30-34 age groups lived in a mobile-only household. King-Fisher Company, inc

  15. VOIP subscribers will surpass PSTN in 2013 US PSTN vs. VoIP Subscribers (M) VoIP Subscribers (%) PSTN is expected to decline at 9 % annually while VoIP grows at 27% Source: In-Sat and Accenture Estimate King-Fisher Company, inc

  16. Sunset of the PSTN • PSTN is already more expensive to maintain than competing services. • As the number of PSTN subscribers continues to decrease the cost of maintaining service increases. • Current trends indicate that by 2018 the PSTN will no longer be viable and will be abandoned as a regulated monopoly. King-Fisher Company, inc

  17. Characteristics of VOIP • Audio is digitized, packetized and included with other data on the IP link. • This can include digital television signals and Internet data. • Audio Bandwidth usually not a problem. • Multiple connections share single physical path. • Statistical Multiplexing combines the calls. • Dropouts are poorly controlled. • Latency is poorly controlled. • Timing is uneven (jitter). King-Fisher Company, inc

  18. Control of VOIP • VOIP over public Internet does not permit control of many parameters. • VOIP over private networks (Cable TV, Fiber Optics) allows parameters to be customized to work with DACTs, but: • Providers attempt to maximize throughput and can decrease performance on the fly. • The only indication that a connection no longer supports DACT is if the daily test fails. • Often the incompatibility is intermittent and may pass the daily test but not work all the time. King-Fisher Company, inc

  19. Other VOIP Concerns • For most VOIP installations the connection depends on the following items at your location: • Computer. • Router. • Data Modem. • Backup Power for these items include UPS and vendor-supplied backup battery. • Total backup time is usually a few hours. King-Fisher Company, inc

  20. What About Cellular Technology? • Current DACTs work poorly over Cellular Telephones. • Special modems have been developed that work well on Cellular Networks. • Cellular networks are likely to be overloaded during even a commonplace disaster. • Many Cellular towers have a maximum of 8 hours of backup power; some have much less. King-Fisher Company, inc

  21. SMS (or “Text Messaging”) • Text messaging would seem to be a natural mode for transmitting alarms. • Cellular carriers do not recommend its use for emergency communications because: • All text messages share the same frequency channel. • Cellular networks do not guarantee timely delivery of text messages. King-Fisher Company, inc

  22. NFPA Regulations • For alarm communications, NFPA regulations strive to meet 3 basic principles: • Alarm delivery must occur within a specified time (End-to-End duration < 90 seconds). • Alarm communications must have at least 2 independent redundant paths available. • Alarms must be detected and delivered up to 24 hours following loss of primary power. King-Fisher Company, inc

  23. NFPA Regulations NFPA Part 72-2010 26.6.3.2.1.4 Transmission Channels. (A) A system employing a DACT shall employ one telephone line (number). In addition, one of the following transmission means shall be employed: (1) A second telephone line (number) (2) A cellular telephone connection (3) A one-way radio system (4) A one-way private radio alarm system (5) A private microwave radio system (6) A two-way RF multiplex system (7) A transmission means complying with 26.6.3.1 King-Fisher Company, inc

  24. NFPA Regulations • Multiple telephone “lines” over a VOIP connection are really different data packets on the same wire. • All data handled by the same electronics. • This does not meet the intent of independent redundantsignal paths as put forth by NFPA. King-Fisher Company, inc

  25. Digital Dialers Make No Sense for the Future • A digital dialer is designed for an analog communications system: • It converts digital messages to analog tones. • If analog tones are transmitted over a digital communications system (VOIP or Cell Phone): • Analog tones are converted to digital bits. • At the other end, digital bits are converted to analog tones. • The digital dialer receiver converts the analog tones to the digital message. • Digital - Analog - Digital - Analog - Digital King-Fisher Company, inc

  26. What Can We Do? • Start replacing Digital Dialers now! • Over the next 6 years, 40 million of these devices must be changed to other technologies. • Replace the redundant telephone line with a different modality, such as radio, for true redundancy. • Look forward to a time when new technology will provide direct digital access to the IP. • Make sure all future IP connections have sufficient backup power to meet NFPA standards. King-Fisher Company, inc

  27. Reliability King-Fisher Company, inc

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