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Security systems are very different than fire alarm systems. According to John Fenske, director of global security product management, Johnson Controls, the main difference is how the systems are adopted. Nowadays, a building cannot be occupied unless a fire alarm system is installed. A security system is not so much of a necessity and usually is installed solely at the owner’s request. However, the main commonality lies in the design process. Every system design should begin at the same place.
Step 1: Imagining
It can be fun to imagine scenarios in which all the building systems talk to each other. It also can be useful. The key is imagining what a system could do and then designing it so that it is feasible and accomplishes the owner’s goals.
With today’s technology, you could conceive science fiction-like scenarios. Someone presents a smart card at the entrance. Within a certain time frame, he or she should be using his or her card to gain entry to his or her workspace and then be turning on the computer. If this doesn’t happen or if someone tries to remotely enter the virtual private network with those credentials, you can pull up video from cameras at strategic points. Or, if there’s a report from the fire alarm system that a certain set of temperature sensors have entered alarm mode, view cameras at that area to see the extent of the fire. Within seconds, you can compile this information and display it superimposed on a 3-D floor plan of the building, so the arriving firefighters will know exactly where to go and what kinds of equipment they will need.
Step 2: Planning
After imagining the possibilities, the hard part is making the practical design decisions. Decisions about integrating the security system can be based on the particular preferences of the management or the integrator. Some users prefer to isolate the security system from the building management system, perhaps running it on the same network, but not integrating it with the other systems. On the other hand, the fire codes mandate certain interactions, such as releasing electrically operated door locks. The National Electrical Code requires that this “integration” be by dropping out a normally closed relay contact in the fire panel to interrupt power to the access controlled egress door lock.
“[The] Code requires that this be hard-wired … fire is the last electrical system to go IP,” said Steve Sachs, sales application engineer, Siemens Industry Inc., Building Technologies.
Sachs described a scenario—a school setting—where the two systems would interact. The facilities manager might want to instantaneously see who activated a pull box after an alarm. This would be implemented by having a contact-transfer in the fire alarm panel signal the workstation in the video system, which would then trigger a camera call-up (or popup) command. That could be done with relay logic or with software in which an interface program could generate an RS-232 serial string. The information generated by the fire alarm control panel would be sent over the Internet to the security system’s software interface. The system software would be programmed, so when it received a certain input, it would cause the image from a particular camera to pop up onto the alarm-monitoring window. On an even more sophisticated setup, there could be an application programming interface (API)—which is custom software often written by a third party—that would be designed to accept inputs from one system and initiate preprogrammed responses in another.
“Although, more frequently, it’s relay logic because not too many people request these features,” Sachs said.
A more common use for popup images is in the integration between the access control and video systems. For example, if there is a door governed by card access, and there is an indication of either forced entry or the door is being held open too long, you’d want an image to pop up so that the facility’s people could immediately see what is actually happening.
The decision of how to implement the interaction has a lot to do with the scale of the system—the size of the building. If it’s a fairly small building, you could easily use relay logic, one relay for each pull box, for example. Going up the scale of sophistication (and cost) is a method that uses a serial RS-232 connection, a standard API and, ultimately, a custom API.
The bottom line
While building integration generally sounds great, it has to be focused before it can be useful. Fenske said that some important questions his company always addresses to its customers are “What are the end results? What are you really trying to achieve?” It seems to me that answering these questions should be the start of the design process.
BROWN is an electrical engineer, technical writer and editor. For many years, he designed high-power electronics systems for industry, research laboratories and government. Reach him at [email protected] or at www.writingengineer.com, an independent professional writing service.