COVER STORY
RFID (radio frequency identification) uses digital data encoded in RFID tags, captured by a sensor via radio waves. Although RFID is used successfully for asset tracking, it is not so suitable for personal attack alarms.
GPS (Global Positioning System) is the satellite-based radio navigation system we all know. Its main limitation for attack alarm systems is that it does not work well indoors.
Cellular radio uses multilateration from multiple base stations to gain a rapid (but rough) idea of a user’s position. It is not sufficiently accurate or reliable to identify a specific room in a building. Far from ideal for a critical attack alarm system!
LIGHT
The third branch of physics that can be used for transmission is light waves.
We can quickly dismiss visible light for two main reasons. One because it relies on ‘line-of-sight’ and two, because there is a massive amount of interference from artificial and natural light.
Infrared (IR) on the other hand is very suitable. Solid surfaces such as walls, ceilings, floors and doors block infrared light, so in effect each room becomes a ‘sealed box’. When a receiver in a room is triggered by an infrared alarm signal, providing the location of that receiver is known, the location of the incident is also known. Absolute simplicity because nothing needs to be calculated.
There is a common misconception that IR requires line-of-sight, but both hard and soſt surfaces reflect infrared well. The signal will bounce off such surfaces and should always reach the receiver. When the optics are correctly designed to optimise both ends of the process, signal transmission and reception, an extremely reliable link can be created.
NETWORKS
In every system, once a receiver has been triggered by an incoming alarm signal, it still has to relay that information to where it can alert the response team. A network is required to link the individual units and permit communication between them.
The Pinpoint system has always been based on distributed processing and broadcast messages on a resilient ring topology network. Importantly, no device on the network is dependent on any intermediate device on the network to raise the alarm. Alarm messages will typically set off visual displays, over door lights, PC screens, smartphone-apps, sirens and any integrated third-party systems.
CONCLUSION
The approach of infrared link, no centralised processing and dedicated ring-topology cabling, appears to provide the simplest and most reliable system for critical personal protection alarm systems.
In the case of our own Pinpoint system this achieves a timescale from activation on the person-worn alarm transmitter to activation of the alerting devices typically in under one tenth of a second. Simplicity, reliability and effectiveness remain the ideals for a safety critical system.
www.pinpoint.ltd.uk/ twitter.com/TomorrowsCare - 13 -
“There is a common
misconception that IR requires line-of-sight, but both hard and
soft surfaces reflect infrared well.”
"
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46
