Security Sales & Integration

September2013

SSI serves security installing contractors providing systems and services; surveillance, access control, biometrics, fire alarm and home control/automation. Coverage in commercial and residential product applications, designs, techniques, operations.

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CHECKING YOUR CONTACTS LIST TECH TALK by Bob Dolph Bob Dolph has served in various technical management and advisory positions in the security industry for 30+ years. To share tips and installation questions, E-mail Bob at bdolph.ssi@gmail.com. Check out his Tech Shack blog at www.securitysales.com/blog. bdolph.ssi@gmail.com One of the most basic elements of an intrusion system is the alarm contact or switch used to secure doors, windows and other building openings. Although ubiquitous and not overly complex, alarm contacts nonetheless require the utmost attention to ensure proper alarm system operations. I t's been a considerable time since we have discussed the important and exciting subject of magnetic alarm contact sensors. Tese small, often inconspicuous components of alarm systems have been around since the beginning of the industry. Te alarm contact, if properly selected and installed, can provide reliable and often stealth detection of openings being breached, devices being moved and building perimeters being compromised. However, if not properly applied and installed, these devices can cause customer complaints of performance frustration, false alarms, and possible missed detection by the alarm system. reliability test begins when these devices are installed by the technician in the feld. If not given the proper respect, the hermetically sealed glass reed enclosures can rupture. In such a case the damaged alarm contact may still perform properly at the time of installation; however, the nowcontaminated metal reed contacts will prematurely, and in many cases intermittently, fail down the road. Can you say service call? In order to avoid these problems I have put together some industry-proven alarm contact installation tips and notes: • For recessed alarm contacts, drill the holes slightly larger so sensors ft loosely in mounting holes. If holes are too snug, the hole may later compress the reed switch and damage it. Tis is especially true in new construction green wood. Use RTV-type silicone to suspend and hold the recessed sensor in the mounting hole. • Use specially designed alarm contacts that prevent hole compression problems. One of my all-time favorites is the Interlogix 1275 Series "wing ft" (formerly Sentrol/GE). Another to try would be the new concept, nonglass Magnasphere devices. • To prevent false alarms on loose-ftting doors, mount the alarm contact closer to the hinge side and/or use wide-gap magnets and switches. • On steel doors, use wide-gap switches or specially insulated alarm contacts such as the Tane SD Series. • Steel will infuence magnetic reed switches to about half GETTING IN CONTACT WITH SWITCH TIPS Te majority of alarm contacts used in alarm systems have one common key component, the glass encapsulated electrical reed switch. Tese reed switches are often coated with deactivated rhodium to prevent the reeds from sticking together after long periods of inactivity in a door or window. Tey are reliable in that they have been performance tested to in excess of 400 million cycles. When assembled in the factory they are often still soldered by hand in respect for the delicate nature of the glass capsules. While we have seen great care taken by manufacturers The Magnasphere alarm contact is a spherical magnet and operates in a defned activation zone diin the assembly of glass reed rected toward the door magnet. This design makes the device highly resistant to defeat and tamper via external magnets. Diagram courtesy Magnasphere switch alarm contacts, the real 44 / SECURITYSALES.COM / SEPTEMBER 2013

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