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TECH TALK TECH TALK When talking about the installation of recessed alarm contacts, I can't think of a better and handier tool than the prewire plugs from Kimball, Neb.-based George Risk Industries (GRI). These handy devices allow you to prewire an alarm system without the need to leave wires coiled in the wall. You can simply predrill the recessed contact location. Pull the alarm loop cable out and loop the stripped end of the cable through the loop in the contact plug. Push the plug back in the mounting hole for future use. When the customer signs up all you need to do is pull out the plug, install the alarm contact and you are done. TOOL TIP the gap in air. To be safe, make the gap distance approximately 25% of the "make" air distance. Use plastic spacers if possible (magnet side f rst). Test performance. • Myth: Applications on steel do NOT drain the magnet. Tey do, however, reduce the magnetic feld. • Magnetic reed contacts exhibit a feature known as hysteresis. Tis simply means that the "make distance" of the pullin action is about 80% of the "break distance" of drop-out action. Tese distances are not equal as many may think. The prewire plugs from GRI (grisk.com) are reusable, cost-effective in meeting prewiring needs. They come in white or black. Photo courtesy George Risk Industries EOLR Installation Tip: A while back I was asked by a Tech Talk reader, who was updating a system with a new alarm panel that had a diferent EOLR requirement, how he could update a nicely concealed alarm contact EOLR without having to pull out the contact. One suggestion was to try using a relay interface with the existing alarm contact using something like the ELK-924 sensitive relay module. Place the alarm loop in line with the relay coil and use the panel's aux power. Te NC alarm loop will keep the relay activated, then use the NO relay contacts for the new NC alarm loop. BEING IN THE LOOP ON LOOPS If you are familiar with the electrical relay terms normally NEW KID JOINS OTHERS ON BLOCK closed and normally open you may f nd alarm contact terms While magnetic activated alarm reed switches have been confusing at frst. Electrically speaking, around the alarm industry since Day a normally open device is the state of One, a new device has been shaking EOLR components a de-energized electrical switch such things up. boost resistance to as in a relay. Tis would account for Te Magnasphere has grown in a normally open (NO) magnetic reed popularity due to its unique and system compromise switch being used in a normally closed patented design. Te device utilizes a (NC) alarm loop. Some in the trade may and provide conductive ball, post and robust metal confuse this issue by referring to a NO enclosure (see diagram). Tis conextra electrical alarm contact as a NC sensor, when fguration provides high resistance to supervision and technically it is a NO device in a NC defeat and tampering. It also provides the ability for alarm loop. Te close proximity of the high resistance to contact welding magnet activates the NO reed switch from lightning. In fact, it is presently systems to report to keep it closed until the devices are listed to the new UL 634 Level 2 High circuit failure from Security Standard, and is used in high separated and an alarm condition occurs. accidental shorting security government installations such I have written before about the as Secure Compartmented Informaor opening of the important of applying end-of-line resistion Facilities (SCIF). Keep an eye out tor (EOLR) supervision to your alarm this fall for a wireless version of the alarm contact contact circuits at the alarm contact. Magnasphere alarm contact. circuit. Tese supervisory components not only Make sure to check with alarm increase resistance to alarm system contact manufacturers such as Tane, compromise, but provide extra electrical supervision and George Risk Industries (GRI) and Interlogix for their spethe ability for your systems to report circuit failure from cialty alarm contacts as they can save you time, money and accidental shorting or opening of the alarm contact circuit. frustration. A couple others that come to mind are the Quick One of the best ways to apply this technology is to order your Switch for storage facilities and the newly released, patented alarm contacts with the appropriate EOLR built in the alarm low-prof le venting magnet contact confguration from contact enclosure. Magalign Inc. 46 / SECURITYSALES.COM / SEPTEMBER 2013