The Home Security Alarm Forum Needs Your Input

This website was created to provide a robust database of information for use by end-users, homeowners and industry professionals alike. Our site is a unique resource, which provides an opportunity for experts in their fields to exchange ideas and information and to share their knowledge and experience with others.

If you have questions regarding your home security alarm system or if you are considering a Do It Yourself project, look through our General Reference Materials and Frequently Asked Questions sections to familiarize yourself with the terminology and components associated with security alarm systems. The DIY Forum's Glossary of Security Related Terms will help beginners understand the terminology found in security system installation manuals. The NBFAA's (National Burglar & Fire Alarm Association) Ten Commandments of Wiring and Minimum Installation Standards are excellent references for professional and beginner alike. Scanning posts on the various forum boards is time well spent. Use the Search feature to find Topics which are of particular interest to you.

Be sure to download manuals for your existing system, the DIY Alarm Forum has manuals for many of the most popular alarm systems available as free downloads for our members. If you are considering a DIY security system project, download manuals for the systems that you are considering and compare features and options before making a purchase. If you don't find the particular manual that you are looking for, just email Tech Support and ask.

Whether you are looking for information on an existing burglar alarm system or DIY systems we hope that, upon exploring our alarm forum, you find the help that you were seeking. If not, please do not hesitate to post your questions; after all, that's what we're all about. We have a large community with volunteer experts from all segments of the security industry willing to assist you with the help you seek.

This alarm forum flourishes because of user generated content and interaction. So, when you receive answers to your questions or find information on our site and apply it to your system or Do It Yourself installation, please come back and let the community know what the results were, your feedback will help others.

The FBI's Preliminary Uniform Crime Report for 2005 shows an increase in violent crimes, murders, property crime, and more pointed, robberies and burglaries across America. The fact is, if you live in a metropolitan area, these crimes are more likely to occur and it is up to you to protect your family and property. Statistics also show that homes without burglar alarm systems are four times more likely to be targeted. We encourage you to avail yourself of the many benefits of a security system; installed professionally or as a Do It Yourself home alarm project it is an investment in personal safety for you and your family.

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If you are considering a home security system but have decided that you have neither the time nor the inclination for a do it yourself project then it's time to find a professional.

Here are some tips to consider when looking for an alarm company:

Call your insurance agent first, most insurance companies offer discounts ranging from 2% to 25% on homeowners' policies when a home is protected by a security system (that should tell you something). Ask how much you could save, which types of systems will qualify you for the greatest savings and see if the agent can offer any referrals.

Check with your state alarm association for referrals to companies in your area. Association members agree to abide by a Code of Ethics and provide quality services.

Ask neighbors, friends and relatives about their experiences and for referrals.

Contact the Better Business Bureau regarding complaints that may have been filed against any of the companies.

Narrow your prospects to 3 or 4 companies; call them to schedule an appointment. Schedule at a time when all members of your household can be present, be sure to ask for the name of the person who will be calling on you and verify their identification upon their arrival.

Ask for an inspection of your premises, a demonstration and a quote in writing. Ask for references and check them later at your convenience.

Ask if the company has all licenses and permits required for your area. Are their technicians licensed and/or certificated? Ask if they screen their employees or conduct background checks before hiring.

Does the company maintain adequate insurance coverage? Do they carry Errors & Omissions?

Will you be given thorough training on the operation of the equipment? Everyone who will be using the system should be present during this training.

READ THE CONTRACT! Does it include everything that you were promised verbally? Does it include a 3-day right of rescission clause? Does it specify what equipment you will own, and what equipment, if any, will remain the property of the security company? Will you be provided with all system codes upon the expiration of the agreement or will they change them and provide you with the new codes? What will they charge for this service call?

Make sure that you understand the terms and conditions of the monitoring agreement. What is the total cost over the life of the contract? What Central Station will be monitoring your account? What are the provisions regarding early termination of the agreement? Is the agreement assignable?

Don't forget to check the references.

Take the time to become an educated consumer. If you have questions at any point in the process don't hesitate to post them on the forum, after all, that's what we're all about.

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End-Of-Line Resistors --- The Basics

What are they, and why are they used?

Early security systems used simple electrical circuits to monitor the status of doors and windows. The circuit was either closed or open, and therefore returned full voltage or no voltage at all to the control panel; that was all the system wanted or needed to know. Although such circuits are still in use today, the digital age gave manufacturers the opportunity to make systems more secure.

A resistor is a small semiconductor which resists the flow of electrical current. The current is permitted to flow, but the voltage is reduced by the value of the resistor. If a resistor is connected, in series, to a sensor on an alarm circuit, then the control panel no longer sees full voltage traveling through the circuit, but rather a reduced voltage, when the circuit is closed. Now there are three possible conditions for the control to measure: zero voltage (if the circuit is open), reduced voltage (if the circuit is closed and secure), and FULL voltage if the wiring has been compromised. For if the two sides of the circuit are making contact at some point between the control and the resistor, the current has a shortcut back to the control, thus bypassing the resistor. The control will see this full voltage as a fault and will alert the user.

Where should resistors be placed?

The method just described can ONLY work if the resistor is placed at the end of the line. There have been many discussions about placing the resistors at the control panel ("in the can," as the professionals say). Although there may be practical reasons for doing this, it must be understood that placing resistors anywhere other than the end of the line does NOTHING to supervise the wiring, which is the stated reason for using resistors. A resistor can only supervise the wiring between the resistor and the control.

Why does the wiring need to be supervised? How can the circuit become shorted?

If a potential burglar were to gain access to the zone wiring, the wires could be deliberately shorted, allowing the burglar access to the building at a later time. Also, a nail or screw (for hanging a painting, photo, etc.) could conceivably pierce both the outer and inner insulation of the wires and make contact between the two conductors. While both of these are admittedly unlikely, they are not impossible.

If a shorted zone is so unlikely, are resistors really necessary?

This question has no simple answer. If it is being asked by a pro installer, there are liability issues to consider, especially if the manufacturer recommends or requires resistors. If a do-it-yourselfer is asking, then no one else can provide a satisfactory answer. A person installing a system in his/her own home must consider the potential risk of compromised wiring and then make an informed decision. Finally, there is also the question of whether a particular system will even allow the elimination of resistors. If it does not, then the only decision would be where to place them. If resistors are required, but wire supervision is deemed unnecessary, they could be placed at the control.

Resistors seem like such a sensible idea. Is there any reason NOT to use them, and place them at the end of the line as required?

There are a couple of reasons. First, although it is usually quite easy to place a resistor inside a motion detector or glass break sensor, connecting one to a magnetic contact can be a trying experience, especially with recessed contacts. The resistor must be spliced to the wire in some way, and the splice must be pushed back through the hole before the contact is inserted (preferably in such a way that it can be removed if necessary). On a surface mounted contact, the resistor and splice will be visible, and (partly depending upon the installer's skill) can be aesthetically obnoxious. Second, in the event that the control panel is replaced at some future date, the resistors will not be the correct value if a different manufacturer's equipment is used. There is not even a guarantee that the same manufacturer won't change resistor values in the future (although this seldom happens). Removing and replacing all the resistors (especially from recessed contacts) in a system has been shown to cause considerable loss of hair, sleeplessness, and outbursts of foul language.

Is there any way to place the resistor inside the can but still supervise the wiring?

Yes. By using a four conductor cable for a two wire sensor, the two free conductors can be used to extend the circuit from the sensor location to the can, through the resistor, and back to the sensor. The resistor would actually be at the end of the line, and supervision would be accomplished.

Are there any other ways in which resistors are used?

Yes. First, fire zones always use resistors, even if the other zones do not. This is because fire sensors are "Normally Open" devices; they only close the circuit when they trip. Therefore, a fire zone in its normal state would appear the same to the system as one where the wire has been cut: namely, open. To prevent this, a resistor is used to close the circuit (with reduced voltage), so that it can be supervised.

Second, some manufacturers allow the use of double EOLR's. In this case, a second resistor is added across the terminals of the sensor, so that is in parallel with the circuit. If you will recall, a single resistor allows the system to sense if the circuit is secure, open, or shorted. The second resistor adds the capability of differentiating between an open sensor and an open, or broken, circuit. Now, if the sensor opens, the current passes through both the series and parallel resistors. The panel senses the reduced voltage and knows that the sensor is, in fact open. With this configuration, zero voltage can mean only one thing: a broken circuit. This constitutes the maximum supervision of zone wiring.

Third, some manufacturers allow the use of "zone doubling," where two zones, each with a different resistor value, are connected in parallel to the same two terminals. Since they are in parallel, the system sees the total of both reduced voltages when both zones are closed. If one opens, that voltage is removed, and because of the different resistors, the system knows which one is open and which remains closed. This effectively doubles the number of zones available on the main board, although it does not change the maximum capacity of the system.

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