News

A Brief History of the Security Alarm

It is 3 a.m., and the dog is sniffing at the back sliding glass door in your dining room. This is your cue to let the dog out to relieve a little built-up 10/01/1998 8:00 AM Eastern

A Brief History of the Security Alarm

Oct 1, 1998 12:00 PM, Steve Filippini




It is 3 a.m., and the dog is sniffing at the back sliding glass door inyour dining room. This is your cue to let the dog out to relieve a littlebuilt-up pressure. As you open the door to let her out, your sleeping brainstruggles to remember what it is you are forgetting to do. The bells andwhistles shrieking from your security system jogs the memory. You have justcreated a false alarm. The first thing you worry about is waking up thefamily. The second thing to worry about is waking up the neighborhood. Whatis sometimes overlooked is worrying about your alarm company's dispatchingthe police to your residence. You make the call to the monitoring center,and after identifying yourself, you cancel the dispatch with a promise thatyou will do better next time.

It is embarrassing, but you are not alone. Everyone who uses a securitysystem has done it, or will do it. It becomes second nature to arm anddisarm your system. It is the change in the daily routine that tags you.The question will come up as to whether or not you want to have yoursecurity system monitored. It seems like such a hassle, why put yourselfthrough it?

Having a security system monitored means that you are willing to pay amonthly fee to a monitoring center. This fee is used to hire people to sitand watch for and react to your security system in the event it calls in toreport an alarm condition. Sound simple? It is.

Most of the security companies on the market today either provide or haveties to a monitoring center. Whether it is a local presence or nationaloperation is not the issue; it is how well they provide the service that isimportant. But first, a little history lesson.

Way back in the days of people much older than I, people would rely onsimple means to alert others of a breach in security. Little bells attachedto a door that rang when it was opened, tin cans tied to a string across apathway, that sort of thing. One day, someone placed a large bell into ametal enclosure and placed four lantern batteries (remember those?) insideof it with a relay and mounted it to the outside of the building. From theenclosure, there were two sets of wires, one for the door contacts and onefor the keyswitch that turned the bell on and off. This technology iscommonly referred to as a "local bell." Maintenance was a snap. Dependingon the usage, these batteries could last up to a year. When the bell rangweakly, you replaced the batteries. The hardest thing I have ever had todeal with when working on one of these was the hundreds of bees and hornetsthat were magically drawn to them.

This simple system used the relay to monitor the door contacts. Thekeyswitch was located outside, and the owner would close all of the doorsand turn the key at night. If the doors were open with the keyswitch on,the bell would ring. Closing the door would not stop the bell; only byturning the key could you silence it. The local bell uses a wiring schemethat latches the relay contacts into an alarm condition.

This was very popular for a while, that is until people figured out thatthe bell could be yanked from the wall and quickly silenced. The other flawwas the locations of some of these businesses were way out in the toolies.The bell could ring all night and bother only the local night critters.

So, someone came up with the idea that a pair of wires from the premisecould be tied into the local police station through the telephone lines.These lines were dedicated to the alarm panel only. In the police station,there was a rack of modules that had dials and meters on them. The securitypanel back at the premise used a series of large resistors, and the policestation had a room with a whole slew of car batteries that pumped voltageon the phone line to create a current source. The resistors would be tunedto send back a specific current level. This level was reflected on thedials at the police department. If the line were to be compromised(cut/bypassed), the dial would drop its reading, and the police would bedispatched. This was referred to as a DLPD (Direct Line Police Department).These systems were popular with managers of jewelry stores andhigh-security-minded business owners. Problem was, a lot of phone lineswere being used up, and the police department was chasing tons of falsealarms on a daily basis.

Next came "McCulloh." Same principle as the DLPD, but with a twist. Insteadof a dedicated pair of phone wires from the premise to the policedepartment, the phone company ran a pair of wires out to a location andallowed multiple premise units to be wired in series with the main feed.The main feed was routed to a secure location, which will be referred to asthe monitoring center from here on (call it what you want, it still had aroom full of car batteries) and tied into a machine with spools of paperand little probes with ink at the end. The premise units were replaced witha device that used a wheel with spokes protruding from it. As the wheelturned, it opened and closed a set of contacts that sent a series of MorseCode-like pulses to the monitoring center. At the monitoring center, eachpulse would cause the probes to release ink onto a thin spool of paper. Forexample, if the premise unit's code wheel had two spokes followed by threespokes followed by one spoke on it, the monitoring center would see linesof ink that when counted, identified premise unit number 2-3-1.

Slick enough, but easy to compromise. If you went to an unsecured premiseunit, cutting the phone line would disable all of the premise units on thatfeed. Another hurdle to overcome---if more than one premise unit tripped atthe same time, you would see a clash of pulses that was hard to decipher.Even more of a concern, maintaining all of those car (later they weremarine) batteries.

The next stepThen came digital communicators. These devices used the same principle as aphone call to the police, but better. The digital communicators would beprogrammed to call a digital receiver at the monitoring center. The premiseunits were assigned a premise number that was programmed into thesedialers. When the alarm tripped, the digital dialer would call the digitalreceiver and report the location and area of protection violated. Thisinformation would be first displayed on a small LED screen, then laterprinted out to a spool of paper for later reference.

No more rooms full of car batteries or dedicated phone lines. With thiscame an added bonus---this also allowed the monitoring center to analyzethe alarm signal before dispatching the police. This reduced the number offalse alarms, much to the relief of the local police officers. One furthernote, the digital dialer was/is able to send alarm signals that alert themonitoring center to dispatch the fire department or paramedics as well.

Since the introduction of digital dialers, the phone company has raised thecost of a dedicated phone line to the point of discouraging furtherrequests for the line. The police departments no longer offer DLPD service,and car battery sales have dropped off significantly. At this point, youwould think all was right with the world.

As the technology grew, so did the ingenuity of the burglar. All they hadto do was cut the phone line. If the line is unprotected, it is just amatter of cutting the right pair that the alarm uses. Actually, they takeout full banks of phone wires, hoping the right pair is included in theresomewhere. Read the papers; you hear about these incidents every now andthen.

Now the need for a backup communicator was needed. How do you make a phonecall without phone lines? You use a cellular dialer to make the call foryou if the normal line is not available. Cellular was expensive at first,but the cost has been coming down as the public embraces cellular phones.There is also a line of long-range radios that can transmit alarm signalsacross the country in seconds. Microwave technology is also used in someareas. If your security installer looks like he or she has a headache, youknow why. As the industry develops better and faster ways to send the alarmsignals, your installer needs to absorb as much of the new stuff aspossible.

Enough of the history lesson. What happens to the alarm signal when itreaches the monitoring center? In today's centers, the signal is routedinto an automation system that has all of your customers' informationstored. The automation system looks at the signal and attaches it to theappropriate customer. From there, the customer's name, address and phonenumbers are at the operator's fingertips. Special instructions requested bythe customer are also displayed, and the operator can then take thenecessary steps to dispatch the correct emergency agencies properly.

Why would you monitor a security system? As tight as you might be with theneighbors, they are not always home to watch the house for you. If yoursecurity system rings the bell on a daily basis, they are going to ignoreit or take out the bell with a sniper's rifle. Monitoring your securitysystem provides peace of mind. In the event of an emergency, it is nice tohave one less thing to remember to do. During a fire, the priority is toget family members out of the house quickly. During a burglar alarm,getting to a phone may not be practical. Let the security system do all thework.

Now, this is when I like to pass on some lessons I have learned over theyears. Let's start with local bells. I mentioned the bees and hornets. Icarried two cans of Raid Insta-Kill everywhere I went. I learned if the bugspray smells like lilacs, it attracts, not repels, angry flying insects. Ialso learned to check the enclosure that is mounted outside of the buildingfor a tamper switch. I once was on top of my work van with a ladder toreach the bell enclosure. As I was removing the locking screws that keptthe lid secure, I had the feeling I was forgetting something. I remembered1/10th of a second before the lid swung open on the enclosure that therewas a tamper switch protecting the alarm, and the bell rang (as it should)in all of its glory. My partner swears I bounced off the hood of the van,but I remember nothing.

Direct wire was another lesson learned. Those car batteries I keepreferring to are wired in series to supply roughly 90 V to 120 V to thephone line. A common practice, in the days of old, was to wire the phoneline through a thin strip of window foil. This foil was glued to the glassaround the outer edge (sometimes the installer would impress us byincluding patterns and designs) of the glass. That way, if the window wasbroken, the foil would tear and open the phone line to alert the police ofa problem. Anyone who has worked with 24-hour foil (that's what it wascalled where I'm from) willagree with me when I say, you do not locate theopen in the foil circuit by licking your thumb and running it along thefoil to find the hairline tear. Trainees do that. Once.

McCulloh taught me that using a metal file to scrape the contacts that openand close the phone line (90 V to 120 V) during an alarm transmission isnot the smartest thing I've ever done. I was working on a panel severalyears ago when I kept getting bitten by the phone line while I was tryingto secure a circuit inside the control panel. I decided that removing thephone line from the safety of the terminals was my only course of action. Ihate getting bitten by electricity. I was careful to remove the wires andextend them away from the control panel to give my hands plenty of room towork. I dropped my screwdriver and as I bent down to pick it up, the openphone line dragged across my sweaty forehead. I saw major blue streaks inmy head as it snapped back at least 2 feet (0.6 m) from my shoulders.

Digital dialers are safer to work on. Although, as many of you know, youdon't hold onto the ends of the phone line when a call is coming in. I hategetting bitten.


Want to read more stories like this?
Get our Free Newsletter Here!
Past Issues
June 2015

May 2015

April 2015

March 2015

February 2015

January 2015

December 2014

November 2014