Alarm Circuits Guide

Author: Ari Erenthal, Published on May 09, 2017

Alarm circuits are a fundamental element of wired burglar systems. Designing the alarm circuit greatly affects its performance. In particular, more efficient circuit designs introduce less resistance and cause fewer false alarms. In this note, we examine:

Alarm Circuits Overviewed

  • ******** **********
  • *** ** ***** ******* *****
  • ***** ** ******* *** ******* ********
  • ********* ** ********
  • *****
  • ***** *******
  • *** *******
  • ******* ********** **************
  • ******** ** ******
  • ********* **********
  • *** **** ********** ** *** ****?
  • *** **** ******* ** *** ****?
  • ***'* ***

***** ******** *** ***** ******* ** ***** ***** *** ******* sensors. **** *** ******* / ********** ** ***** ***** ** broken (*.*., ** ******* ****** *****), *** ***** ** ********* if *** ****** ** ***** / *******.

How ** ***** ******* *****

** ***** ******* ******** ** * **** ** ***** ******* from ** ***** ***** ** * ******, **** ** * magnetic *******. ********** ****** ***** **** *** ******** ********, **** one ****, *** **** *** ******. **** ********* ****** *** sensor ** *****, ** ********* *** *******, ******** *** ****** to **** **** *** ***** **** *** **** ** *** negative ******** ** *** *****.

** *** **** ** *** *******, *** ******* ** ******** because *** ****** ****** *** ***** ** *****, ******** ******* to **** **** *** **** ** *** ******** **** ** the ******* ** *** **** ** *** ******** ****.

***** * **** ** ***** ** ******* **** ***** ** the ****** ** **** ********* ** *** ***** ******* * large ******, ***** ** ***** *** **************** ****. *** ********* **** ****** *** ****** **** *******, from *** ******** ******** ** *** *****, ******* *** ******, and **** ** *** ******** ********. ******* *** ****** **** cause *** **** ** ********, ***** **** ***** *** ****** and **** *** **** ** *********. ** ***** *****, ******* a ****** **** ****** ****** *******. ** ** **** **** ******* **** ****** ** ***** condition.

Loops ** *******

*** *** **** ****** **** ** *** ******** ******* ** circuits ** ** *****************.

***** *** ********* ******* ** ******* * ***** *******, ***** means **** **********, ***** ****** ** ******* *** ****** ** install. *******, ***** *** **** ********* ** **** ** *** construction ***** *** ********** *** *** ******* ** *** ***** and ***** ******* *** ****** ****** ****** *** ******* ** installed. ********* ******** ************ **** *** ******* ********** ** *** carpenter. *** ***** ******* ***** ** ** **** ** ******** a ********** ** ******** *** ****** ****** *** ******* **** is ********* ** ***** ********** *******, *** *** ********* ****** be **** ***** ** ***** ***** ** *** ******** ** window *****.

******* ****** ** ********* ******* **** *** ********** *** *** more **** ********* ** *******. *******, ****** ****** ** ******* homes ** ********** ********* ******* **** ***** ** ** *** feasible ** **** *** ******** ** *** * ****** *******.

*** ***** ** ******** ******: ***** ****** *** *** (**-***-***) splice. *** ******** ** ***** ******* *** ***** ***** ******* resistance *** ***** **** ****, *** ** ******** * **** skilled ********** ** **** *** ******. ** ********, *** ******* are ****** ** ************, **** ***** ********* ****** ** ******* and **** *** ** **** ** * **** *********** *********, but **** **** ****** ***** ******* ********** *** ******* ** installer ** **** *** * **** ** **** ********** ******.

Loops *********

*** ***** ***** ***** ** ******* ** * **** **** allows *** ******* ** ***** * *******. ******* ****** *** top **** ** *** ****** **** ** ****** *** ***** window ** **** ****** **** ***** *** **** **** ** open. ** ********** ****, * ********** **** * ****** **** from *** ******* ** *******, ******** *** ******* ** ****** around *** ******* ** * ******. *** ********** ****** * loop ** ***** ******, ***** **** ***** *** ******* ** one **** ** *** ******* *** *** *** *****.

*** **** ** *** **** **** ** *** ****** ** the *****, *** *** ***** **** ** *** ****** ** the ****. *** ********** *** *** ***** ** ***** **** one **** ** *** ******* ** *** *****. *** **** of *** ******* ** *** *** ***** ****** *** * loop ******* ** *** **** ** *** ******* ** *** left (***** ** ***** *****). *** **** ******* *** *** left ******* *** *** ****** **** ******* (***** ** *** below) ********* *** ******, ** **** ** *** *** ******* are ******.

Field *******

* ***** ****** ** *** **** ** **** ** *** device *** ** *** ****, ******* ** *** ****** ******. A ******* ********** *** **** * ***** ****** ** *** conditions *** *****. ******* **** ** ********** *** ****** ***************, so * ***** ****** *** **** ** **** ** ***** is ********* ** **** **** **** **** ****** ****. *** example, **** ****** *******, * ********** *** ****** *** **** to *** ********* ** *** ***** ** ********, *** ** sight *** ****** ***** ** ** *********** ***** **************. ***** installers ******** **** *** ****** *** ******* ** * ******** to * ****** *******, *** **** ***** ******* ****** *** siren ***.

** **** *******, * **** ** ***** (*****) ** ******* to *** ***** *****. *** ***** *** ******* ** ******** contacts ** *** ****** **** *** *** *** **** ** the ***** ******, *** **** ***** *** ******* ** *** top **** *** *** ****** **** ** *** **** ******. One *** **** ** ******* ** *** **** ****, ******* one *** **** *** *** **** **** ** ** ******* to *** ***** *****.

ITB *******

*** *******, ****-***-**********, *** ***** ********** *** ***** ***. ******** ***** *** *** ** **** ********** *******, *** they *** **** ****** ** ** *** ***** ***** * splice.

*** ******* *** **** ****** *** ************* ***********, *** **** faster ** **** **. ****** *** *******, *** ***** *******, to *** *** ******* ** **** *****, ** ****** **** making * ****** ** ***** *********** *** **** ******** *** how ** **** **** ****. **** *** **** **** ****** to ************ ** ******** ******* ** *** ***, ******* * troubleshooter *** ******* ******* *** ******* ****** ******* *** *****, and **** *** **** ** ***** **** *** ******** *** splice. *******, ******* ********** ***** ** **** **** ***** *********, and **** **** ****.

Circuit ********** **************

*** ******* ** ** *****, ********* ********* ******* **** ** contacts, ******* * ******** ****** ** ****** ******* ******* *** wires ** * ******** ***** *** ******** ** ** **** not ****.

***** ******* *** * *******, *******, *** ********** *****:

  • ******* ** ******** ** ***** (*).
  • ******* ** ******** ** **** (*).
  • ********** ** ******** ** **** (Ω).

********* * *********** ** *** **** *********** ** ********* *** use. ***** ****** ***** *** ****** ** ******* ** ******** to *******.

  • ** ***** *** *** *****, *** ****** **** ****** *** power ** ** **** **** ***********.
  • ** ***** *** **** *****, ** **** ****** **** **** or ********.

********* *** ******** ** ***** *** ****** *****. *** ******* consume, ******, *********** ** * ************* ****.

  • *** ****** **** *** ***** *** ****** ** **** ****** to **** *******, ***** ***** ***** ** ** ****** **** down, ********, ** **** ***********.
  • *** **** **** ** *** ******* ** *** ****** ****** draw **** ******* **** ** *** ***.

********** ** ******** **** ***** *** *******. ******* **** ******** resistance ***

  • ****** ** ********* *******
  • **** ******
  • *******
  • ****
  • ****** ***********

*** **** ********** ** * ******* **** ***** *** *******, making ** **** ********* *** *** ***** ** ******* *** zone ********. ***** ********** ********* ** *** ******** ** **** goes **, ********** ******** ******** **** * **** *********** ** causing ***** ****** ***** ***** ***** *********. *********, ***** ****** should ** **** ** **** *** ********** ** *** ** possible.

Parallel ****** ******

*** *** ******* ** ******* ******** ******** ** * ****** circuit *** ******** *** ******. ******* *** ****** ** ******* ************ ********** **** *****. ******** ***** ******** ******* *** ****** ******** circuits, *** ******** ***** ****** ******* *** ****** ****** ********.

** ******* ******, *** ** *** **** ** ***** ** ******* ** one *** **** **** **. **** ***, ** ****** *** many ***** ** ***** *** *****, *** *** ****** ** two ***** **** *** ****** ** ******* ** *** ***** terminals. ** *******, **** ** ***** *** ******* ** **** other. **** ***** *************** *******, ******* * ********** *** ****** test * ****** ****** ** *** ******* ** * ****. Series ** ********* **** *** ********** * ***** ****** ** devices ** * *******. ** ** ****** *** ****** ** wire **. *** ******** ** **** ****** ********** * *** more ********** ** *** **** ******* *** *********.

** ******* *******, *** ***** **** **** ****** ** *** ******* **** be ******* ******** ***** *** ***** *** ******* ** ******** are ****. ***** ****** ********** **** ** ********* ** *** screw *********, ***** *** ******* '****' ** *** ***, *** connected ** ******** *** **** *****. ** ****** *** **** devices *** ***** *** ********* ** *** *******, ***** **** always ** **** *** **** ** ******* ** *** ******** and *** ** ******* ** *** ********.

******** ********** ********* **** *** ********** * ***** ****** ** ******* to * ****** *******, ** *** ******** **** **** **** of *****. ** ******* ******* *** ****** ** **********, ******** those ***** ******* ** ******* ** ** *********. *******, ** is ****** / **** *********** ** *********, **** *** **** if **** ***********, *** ** **** ********* ** ************ ***** on.

** * ******** *******, *** *** ******** ***** ** *** wire ***** *** ****** ******* ********, **** *** *** ****** being *** ***** **** ******. **** *** ** * ********* to ******* ** ***** *********. ** ***** ** ************ *** wire ***** ** * ****** ** *** *******, * ********** must ***** **** *** ****** ******.

*********** ***** *********** ******* * '****' *** **** ** ****** devices ** ******** *** **** ** ****** ** ******. *******, the *** *********** ** ****: **** * ****** ****** **** result ** *** **** **********, * ******** ****** **** ** used. ****** ******** ********, *********** *** **** * ******* ** order ** ********* *** ****** ** ********** *******.

Measuring **********

********** ** ******** ***** * ******* **********, ** ***. ** measure **********, **** *** ******** **** ** ***** ** *** Ω (****) ******, *** ***** *** ***** ** *** **** wires ** *** *******. *********** ******* ********** ** ***** **

  • **** **** *** ******* ** * ******* *** *********** ********
  • ****** ******* ** **** ******* ** * **** ** ** split **** ** ***** ******** *****
  • ****** ******* * ******* ****** ** ***** ** ****** ** in ********
  • ****** * ******** ********** ** *** **** ** ************
  • ************, ** * **** **** * ********** ******* **** **** baseline *** ******** * ****** **** ** ********* ******

How **** ********** ** *** ****?

***** ** ** ***** ****** ** *** ******* ****** ** devices, *** ************ *** ******* ****** ** **********, **** ****** be ********* ** * ****** ********* *******. ** * ******* rule ** *****, **** ********** *** ** **** *** ******** resistance ** * ****** ******* ** ~**Ω. ******** **** *** resistance **** ********** ***** ** **** ****, ********* ** *** number *** ****** ** ******* ********* ** *** *******, *** number *** ****** ** ******* ** *** ****, *** ***** composition ** *** ****, *** **** *** ***********, ***** ***** cause *** **** ** ******* ****** ** ******. *** ********* animation ***** *** ******* ******* *** **** ******* *** ***** to *** *******:

********* ***** ***** ************* **** ********* ********* *** **** *********** an ***** *********, *** *** ***** ********* *** ***** ** the ***** ******* *** ********** ** * **** *******. ** a ******* *** * ******* ************* ****** **** **Ω, ******** either ***** * ******** ****** ** ********* *** ****, ******** some ******* **** *** **** *** ****** **** ** * new ****.

**** ********** ****** *** ******* ******* ** ****** **** ** decide ** ***** *** **** ***** **. ** ******* **** been ***** ******** ***** **** ***** ** ***** *******, **** is *** ********.

How **** ******* ** *** ****?

** ******, ** ********* *** ******* *** *** ***** ** a ****** ****, *** *** ******* ** ******* ****, *** the ****** ********* ** * ***** ****, *** ** *****. However, **** ** ***** ** *********** *** ** ***** ** alarm. *** **** ******* *** ** * ****** ****, *** harder ** **** ** *** *** **** ** ****** *** which ****** ** ******* *** **** ** ** ****.

** *** *** ******* ** * **** *** ** * single ****, *** **** **** **** ** ***** *** ** them ****** ***** **** ** *** *** ******. ** * user ***** ** **** * ****** ****** **** ***** ****** the **** ** *** ******, **** ***** **** ** ****** all *** ******* ** *** ****, ***** ** * ****** security **** **** ****** ********* * ****** ******. ** ******* station ***** ** ******** ****** ** **** ** *** ****'* site, **** **** **** ** **** ** **** * ***** description ** *** ******** ** *** *******, *** * ******** location.

**** ****** *** **** ****** * ******* ****** ** ***** out ** *** ***. ***** ********** ***** ******** ********** *** installing **** *********, ***** *** ** *** ******* **** ** the ************. ***** ******** **** ********* *** ******* ****** * second ***, ***** ******** **** ** *** ****. *** ******** of **** ** ******* ******* ** * ****** **** *** when ** ******** ******* **** ******** ***** *** ** **** answer, *** ******* ******* **** **********.

Wiring ******

****** ****** ** ******** ********* **** ****** ***** ***** *******.

  • ****** *** ***** ** *****, *** ***** **** *** ***** alarm *******
  • ***** *** * ******* ** *** **** * ***** * device*******
  • ***** * ******* ** *** **** ***** * **********
  • **** ****** *** ***** ** ** *****

**** ****** **** **** * ****** ***** ******. *******, **** applications **** *** *** ****** ** ** ***** ** **** sirens **** ** ******. *** *******, * ***** ******* ******* would ***** ******* ****** ** ******** ** * **** *****, but ***** ** ********* *** ************ ********. ** ***** ** have ********* ******* **** * ****** ******, ********** *** ****** to **** ****** ** ****** ******** (*** ****** ******) ** in ****** (*** ***** ******). **** *** **** ****** ** wire **** ****** ** ******** *** ***** ****** ** ******. The ****** ** ****** **** **** ********** **** *** ****** in ********, ** **** ***** ** **** **********, *** ********* fewer *****, ******* *** ***** ** ***** ** * ***** volume.

***** ***** ****** ** * ******* ************ ** ***'* ***.

Ohm's ***

************* ***'* *** ***** ***** *************** **** ******. ***'* *** states **** ***** ** * ****** ************ ******* *****, ****, and ****, ************ **** ***** ****** **** ***** ****. **** is **** ******* ** *****, *** **** ** ***** ******* by ****. ****** ********** (****) ***** *** ******* (****) ** down, *** ****** ******* (****) ***** *** ********** (****) ** down.

*** ******** *** ** ******** ** ******* *** ***** ********* to *** ***** ** ** ******* ** ******** *** **********. This ****** ** ****** *** ****** ** ********* *****, ***** in **** ******* *** ********* ** *** *****.

************* ***'* *** *** **** * ********** ******** *** ****** power ********, *******, ********, *** *******. ******** * ****** **** series ** ********, ********* * ***** ****** *** *** **** outputs *** **** ******* ** * ****** ********, ** ****** a ******** *** *** ****** ******* **** ** ********* *** once **** ********** *** ***'* *** *****.

Comments (9)

Nice GIFs! Good Read.

Nice report

Now let's start describing the various circuit types. Class A, Class B, Style Y, Style Z

Thanks, very informative

Next wil nice too read about EOL resistors, resistor guide

how to change resistance using more then 1 resistor parallel or series

I'm quiet surprised how the DEOL not came to the picture in this article. DEOL is only 2 wire for a zone, which is really helpful if you plan a system, and its wiring.

One sensor --> One zone. In the past 15 years I have never broke this rule. Many times the cheap series makes hard to find a contact issue caused alarm, and many times the junction boxes tamper switchs can cause sabotage fails. So this is the really-really basic, and never ever use paralells or series. Especially that zone expanders are cheap as hell. :)

I fully agree that a single device on a single zone is the simplest and best design. However, it is not always practical, it is not always possible, and, due to the large base of installations that have not followed this principle, it is important for installers to understand multi-device circuits in order to troubleshoot them.

First, it is not always practical to dedicate a single zone to every single device when you have a large number of devices clustered together. For example, say you've got a bank of double hung windows, like this:

You could run six wires and dedicate six zones to each contact, but it would be far more practical for the installer and far easier on the user to dedicate a single zone to the contacts (and one more for the acoustic glassbreak detector). This way, the alarm user would have to check to see if one of the "dining room windows" were open instead of having to remember which window was number 39, or what have you.

Second, it is not always possible to dedicate zones to every single device. I've been installing alarms in homes since well before zone expanders were cheap or even available, and even today, not every panel can accommodate enough zones to dedicate a zone for every device. The Vista 20P, for example, can only accommodate 48 zones- more than enough for a small home but not quite enough for a large one.

I'm having a difficult time estimating the 'average' number of windows in a house, but this website for window washers suggests that the average 3,000 square foot house has 30 windows on average, which sounds about right to me. If those windows are double hung, that's 60 magnetic contacts, not including glassbreaks, motions, or doors.

I'm aware that larger panels exist, but they are more expensive than the smaller ones.

Third, even if you try and dedicate zones today- which, again, is always the best way to go, if possible- there is an enormous number of alarm systems installed and in place that were designed before zone expanders were common. Therefore, it is necessary for an alarm technician to know and understand how to troubleshoot these older systems, which in many cases are still functional and still generating RMR in the form of a monitoring contract.

Fortunatelly here in Europe, we don't have these "nightmare" type windows :) So 1 magnet can do the job for us. But in this case, I again miss the DEOL, and with a junction box (even hidden) this can be done at the window side, and the zone is secured (from sabotage) and can give signal, via 2 wire only.

In the old days, we many times offered Galaxy 60 panels for larger homes, and in one case we deployed an 512, it was so huge. Nowdays here we have several very nice "low budget" high capacity 64-128-256 zone alarm panels here, and there is solution as well to handle them within a network. A 64 zone panel is around 100USD, with 16 zones onboard, and with really advanced features. If you want this in EN 50131 Grade3 its 150USD. The 256zone brother is around 200USD. So really don't need to think too much about, how you resolve an issue like you mentioned above.

100% could not agree more, you hit the nail on the head Sir.

As a former service technician working on equipment installed in the 80's having multiple devices on one circuit is quite aggravating when trying to troubleshoot false alarms, especially the old window bugs or window foil. Now when systems were installed back then, say the Moose 735/235 there wasn't much choice. In this day and age their really is no excuse for having more than one device on a zone other than say a double door. Zone expanders aren't that expensive and wireless is extremely reliable these days especially the battery life. I installed my first residential system in over 10 years last summer for one of our good commercial customers and I hardwired everything except for the windows. Man what a pain in the arse. The house was only 75% gutted so the prewire was a nightmare as the house had no real chase between basement and attic and the fact there was not air conditioning and it was over a 100 degrees that week. My point is everything was wired separately as I didn't want the next technician to come out when a glass break started falsing and have to figure out which one it was on a circuit of 10. Also I put the EOLR's at each device as well. I will say after doing commercial work for so many years this was my best looking panel install I ever did thanks to some Panduit. Also with the new low current sirens out there really is no need to use speakers and a siren driver anymore either. Good knowledge for those who don't know how to series parallel though. Anyways just my two cents.

Login to read this IPVM report.
Why do I need to log in?
IPVM conducts unique testing and research funded by member's payments enabling us to offer the most independent, accurate and in-depth information.

Related Reports

Access Control Course Spring 2019 - Last Chance on Apr 19, 2019
Register for the Spring Access Control Course. IPVM offers the most comprehensive access control course in the industry. Unlike manufacturer...
Riser vs Plenum Cabling Explained on Apr 18, 2019
You could be spending twice as much for cable as you need. The difference between 'plenum' rated cable and 'riser' rated cable is subtle, but the...
Axis Supports HD Analog on Apr 15, 2019
In 2017, Axis declared 'Everything is IP': Now, in 2019, Axis has released support for HD analog, with their new encoders.  Why the change?...
Pole Mount Camera Installation Guide on Apr 11, 2019
Poles are a popular but challenging choice for deploying surveillance cameras outdoors. Poles are indispensable for putting cameras at the right...
UK Installer CCTV Aware - Flat Pricing, No Salespeople on Apr 10, 2019
This is a different kind of company. They do flat pricing, they do not have any salespeople and 50% of their sales are sold and booked...
Spring 2019 IP Networking Course- Register Now on Apr 04, 2019
Register now for the Spring 2019 IP Networking course here. Just $299 for the course. This is the only networking course designed specifically...
Bezos-Funded Deep Sentinel Tested on Mar 28, 2019
Backed by Jeff Bezos, the Silicon Valley startup, Deep Sentinel, has declared: No One Does Home Security Like We Do Our Surveillance Team has...
Casino Security Consultant Carl Lindgren Interview on Mar 26, 2019
For more than 20 years, Carl Lindgren worked as a casino surveillance pro, while being active (and sometimes outspoken) on various online video...
Outdoor Camera Installation Guide on Mar 25, 2019
Outdoor camera installation can be fraught with problems. Creating a sturdy and weather tight mount is key for camera performance and longevity,...
Large Hospital Security End User Interview on Mar 21, 2019
This large single-state healthcare system consists of many hospitals, and hundreds of health parks, private practices, urgent care facilities, and...

Most Recent Industry Reports

H.265 Usage Statistics on Apr 19, 2019
H.265 has been available in IP cameras for more than 5 years and, in the past few years, the number of manufacturers supporting this codec has...
ACRE Acquires RS2, Explains Acquisition Strategy on Apr 19, 2019
ACRE continues to buy, now acquiring RS2, just 5 months after buying Open Options. One is a small access control manufacturer from Texas, the...
Access Control Course Spring 2019 - Last Chance on Apr 19, 2019
Register for the Spring Access Control Course. IPVM offers the most comprehensive access control course in the industry. Unlike manufacturer...
Riser vs Plenum Cabling Explained on Apr 18, 2019
You could be spending twice as much for cable as you need. The difference between 'plenum' rated cable and 'riser' rated cable is subtle, but the...
Verint Victimized By Ransomware on Apr 18, 2019
Verint, which is best known in the physical security industry for video surveillance but has built a sizeable cybersecurity business as well, was...
Milestone Drops IFSEC on Apr 18, 2019
Milestone has dropped out of Europe's largest annual security trade show (IFSEC 2019), telling IPVM that they "have found that IFSEC in EMEA no...
The Fastest Growing Video Surveillance Sales Organization Ever - Verkada on Apr 17, 2019
Verkada has the fastest growing video surveillance sales organization ever. In less than 2 years, they already have more salespeople in the US...
Door Operators Access Control Tutorial on Apr 17, 2019
Doors equipped with door operators, specialty devices that automate opening and closing, tend to be quite complex. The mechanisms needed to...
Securadyne CEO: IPVM 'Entertaining For An Ignorant Few' on Apr 16, 2019
Securadyne's CEO Carey Boethel is unhappy with IPVM's report - Failed Integrator Rollup, Securadyne Sells to Guard Giant Allied. Indeed, he...
Dahua Repositionable IR Multi-Imager Camera Tested on Apr 16, 2019
Dahua has released their first repositionable multi-imager camera, the Multi-Flex 4x2MP, claiming integrated IR, true WDR, and flexible...

The world's leading video surveillance information source, IPVM provides the best reporting, testing and training for 10,000+ members globally. Dedicated to independent and objective information, we uniquely refuse any and all advertisements, sponsorship and consulting from manufacturers.

About | FAQ | Contact