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

Testing Bandwidth vs. Frame Rate on Jan 23, 2019
Selecting frame rate has a major impact on surveillance bandwidth and storage consumption. But with smart codecs now common and cameras more...
Bosch Favorability Results 2019 on Jan 23, 2019
Bosch's favorability moderately strengthed, in new IPVM integrator statistics over their results from 2017, with 2019 results showing strong net...
Cable Trenching for Surveillance on Jan 21, 2019
Trenching cable for surveillance is surprisingly complex. While using shovels, picks, and hoes is not advanced technology, the proper planning,...
Mobile Surveillance Trailers Guide on Jan 17, 2019
Putting cameras in a place for temporary surveillance where power and communications are not readily available can be complicated and expensive....
Testing Bandwidth Vs. Low Light on Jan 16, 2019
Nighttime bandwidth spikes are a major concern in video surveillance. Many calculate bandwidth as a single 24/7 number, but bit rates vary...
Access Control Records Maintenance Guide on Jan 16, 2019
Weeding out old entries, turning off unused credentials, and updating who carries which credentials is as important as to maintaining security as...
Access Control Cabling Tutorial on Jan 15, 2019
Access Control is only as reliable as its cables. While this aspect lacks the sexiness of other components, it remains a vital part of every...
Bad: Dahua Villa Video Doorbell Tested on Jan 11, 2019
Doorbells are one of the hottest segments in the residential market but Dahua's Villa Video Doorbell is the worst we have tested.   We bought and...
Winter 2019 IP Networking Course on Jan 10, 2019
Today is the last day to register for the Winter 2019 IP Networking course. This is the only networking course designed specifically for video...
CES 2019 Show Report on Jan 10, 2019
IPVM was at CES 2019 for the second year (see our CES 2018 Show Final Report) and is reporting on announcements and interesting news from the show...

Most Recent Industry Reports

Testing Bandwidth vs. Frame Rate on Jan 23, 2019
Selecting frame rate has a major impact on surveillance bandwidth and storage consumption. But with smart codecs now common and cameras more...
Camera Course January 2019 on Jan 23, 2019
This is the only independent surveillance camera course, based on in-depth product and technology testing. Lots of manufacturer training exists...
Bosch Favorability Results 2019 on Jan 23, 2019
Bosch's favorability moderately strengthed, in new IPVM integrator statistics over their results from 2017, with 2019 results showing strong net...
Intersec 2019 Show Report on Jan 23, 2019
The 2019 Intersec show, held annually in Dubai, is now complete. IPVM attended for 3 days, interviewing numerous Chinese and Western video...
2019 Camera Book Released on Jan 22, 2019
This is the best, most comprehensive security camera training in the world, based on our unprecedented testing. Now, all IPVM PRO Members can get...
Milesight Company Profile on Jan 22, 2019
Milesight Technology, a Chinese company building an International branded business, says they are slowly building their presence through a series...
Cable Trenching for Surveillance on Jan 21, 2019
Trenching cable for surveillance is surprisingly complex. While using shovels, picks, and hoes is not advanced technology, the proper planning,...
Milestone Favorability Results 2019 on Jan 21, 2019
Milestone's favorability moderately strengthed, in new IPVM integrator statistics over their results from 2016. While the industry has been...
The IP Camera Lock-In Trend: Meraki and Verkada on Jan 18, 2019
Open systems and interoperability have become core features of video surveillance systems, as virtually all professional IP cameras integrate with...
NYPD Refutes False SCMP Hikvision Story on Jan 18, 2019
The NYPD has refuted the SCMP Hikvision story, the Voice of America has reported. On January 11, 2018, the SCMP alleged that the NYPD was using...

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