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Joined: Apr 2014
Posts: 4
New Member
Hi there.

Its been a week since this Alarm Horn Fault (Sounder Fault) appeared in my Siemens FC10 alarm panel.

It appeared after I triggered the alarm through smoke tests just for inspection. After I resetted it, the this fault came. I tried to search for various ways how to troubleshoot this one until I reached to check the sounders itself.

Removed all the sounders from the terminating panel (I have 3 installed) and checked each terminals whether they are giving the correct voltage. All the 3 terminals rated 5Vdc. So I concluded its fine. Then I placed the sounders back, and checked the Vdc with it terminated to the panel. I found 2 sounders giving 5Vdc after I placed that back, and the other sounder was giving only 1Vdc. Thinking the sounder itself might be the problem, I interchanged the sounders one by one, but still that certain point was giving 1Vdc. I then went to my uncle's house because we have the same panel and set of sounders and checked the output of his, finding 1Vdc (sounder already terminated). In this case, can we say that the problem is the sounder?

How to fix this problem sir and what might be the cause? Help please. frown

Last edited by Melvin_Melvins; 04/17/14 10:11 AM.
Joined: Jun 2004
Posts: 1,273
The problem is almost certainly NOT in your horns. ('Sounders'... Out my way horns are horns, strobes are strobes; both are part of the annunciator circuit.)

[Forgive me if this is insultingly basic, but you've only posted once... I can't even tell if you've been testing VDC at the correct spot, or much else.]


Fire Alarm logic is split in two:

The annunciator circuit -- aka notification appliances:

Dial out trouble call logic

The detection circuit -- aka alarm or trouble detectors:

Pull stations
Smoke detectors
Heat detectors
Flow detectors (sprinklered spaces)
Pressure detectors
Intrusion detectors (as in someone is turning the water supply to the sprinkler system off)
Circuit fault detection -- terminating resistors are (logically) critical here.
[Not an exhaustive list.]

Some do double duty and have

Perimeter detectors (anti-burglary)
Loss of (ground-link) data-com (paranoid owner-operator)

Troubles in the detection circuit can seem to lie in the annunciator circuit, causing you to chase your tail. Beware.

You've just tested the detection circuit with smoke -- and are now alarmed about the annunciator circuit. That's ODD.


After a test, one has to be concerned with the detection circuit 'latching up.' This can happen if smoke is not purged from the tested device. It will keep tripping into fault or alarm mode.

It's easy to foul up the terminating resistor -- at almost any time. These are used (typically) at the end of every circuit: detection or notification. They permit opens and shorts to become instantly obvious back at the panel -- triggering a trouble call or a raging alarm, depending.

As for VDC readings, I've never seen them used to figure out what's going awry.(much)

Your OP left out a ton of details that you presume we must know:

How many detection zones? Must assume just the one.

How many notification zones? Must assume just the one.

Does bypassing a given device clear up the trouble fault. (Don't swap them around in the system. That gets you absolutely nowhere.) You need to jumper past -- drop out -- a suspected device. (Still need the terminating resistor.)

Is the area really hot? Dusty? Did you clean out the tested smoke alarm? Really clean it out? Did you over do it when testing? Is the device old?

Is your field wiring ship-shape? (I've seen lousy wiring jobs trigger NO END of wasted energy. The offending installer does not see his work as being all that sloppy, of course not.)


Fire Alarm systems balance on a razor's edge. The field craft must be first rate. (The circuits will detect any current bleed -- such as a stray strand touching a circuit board.) The terminating resistor must be in perfect condition -- with no frayed termination. (I've seen work wherein the resistor was broken -- but looked okay -- until you touched it -- barely. Then it popped open.)

What was the polarity of the VDC when you tested? (You do realize that the system goes into alarm by REVERSING the VDC polarity in the annunciator circuit. Said reversal causes the current to no longer trickle past diodes -- but to flood across the horns and strobes -- which causes the VDC to PLUNGE.)

Perhaps you have two zones?

Did you install the system?

Are you looking at the documentation left behind?

Is this your first attempt at a fire alarm circuit?

Do you have any of the trick test equipment used for same?

Were your tests taken with a DMM or an analog meter? (Simpsons?)

Was your system firing off? Or was it firing off and the horns and strobes suppressed by control panel override?

Joined: Dec 2009
Posts: 23
Many alarm systems also do some 'detection' on the 'annunciator' side - monitoring mainly that there IS a load of some kind and that it's not shorted. I don't do fire alarms, but I've encountered this on a number of burglar alarms, and have also seen the effects on a fire alarm panel.

I couldn't find a manual for a Siemens FC10, but I did find a good sample:

Page 11 is relevant: the "sounders" are polarized so as to appear open-circuit when reversed, and are installed in a string with a 10K resistor at the end of it. Applying sufficient DC voltage in the "correct" polarity powers them (and makes noise), whereas a low voltage or "reversed" dc voltage sees only the 10K resistor at the end of the line. Thus the panel knows if the line gets severed somewhere.

OP has 5V at two of his "sounders" and nothing at the third. I'd say the line is severed between the second and third, the terminating resistor being on (or after) the third. Solution? Find and mend the severed wire/connection.

I'd question OP's qualification, but I'm not even sure what the requirements/qualifications ARE in Kuwait!

Last edited by emolatur; 04/21/14 12:47 AM. Reason: omitted something
Joined: Apr 2014
Posts: 4
New Member
As per overall checkup, there is no EOL device connected at the panel. The sounders feed and return to the panel have 2 wires each, means 4. Since it is 4-wired, its a class A connection right?

Here's what i did.

I tried shorting the loop cables (the 4 cables) into +A to +B and -A to -B, and powered the system again. What I did was just testing whether the panel itself or the notification devices are faulty.

Result: The alarm horn fault still persists. Nothing happened so I conclude that it might be a panel problem.

Knowing that the EOL might be in the panel itself (since it is not visually connected), I thought of it as a panel-mounted so I tried ohm-metering the -A and -B. I found a 1942 ohms resistance. The +A and +B is obviously shorted.

The question is:

Am I in the right track of troubleshooting?

What about the variation of Vdc outputs of the sounders to the other?

How to identify an EOL in a class A connection?

Joined: Apr 2014
Posts: 4
New Member
How many detection zones?
---> There are 2 zones, each having 10 detectors each.

How many notification zones?
---> There are 3 sounders.

Is the area really hot? Dusty? Did you clean out the tested smoke alarm? Really clean it out? Did you over do it when testing? Is the device old?
---> It is 3 years old sir and as per checkup, all detectors are clean-as-new. It is not hot here because the place is well ventilated and air-conditioned.

Does bypassing a given device clear up the trouble fault.
---> No sir. The fault still persists.

Is your field wiring ship-shape?
---> I suppose that the wiring is good since no one has ever pulled it off, until now (when I started to trouble)

What was the polarity of the VDC when you tested?
---> It is forward biased sir since a signal can pass when the panel is turned on.

Did you install the system?
---> The Siemens F/A technician did.

Is this your first attempt at a fire alarm circuit?
---> Yes sir and I wanted to figure out this one just for the sake of knowledge in f/a.

Do you have any of the trick test equipment used for same?
---> Only a multimeter sir.

Were your tests taken with a DMM or an analog meter?
---> DMM.


Based on the logic of sounders in my system, no sounder where found having a resistor installed. All are terminated into 2 terminals, having +A -A and +B -B separately. I popped up my unlce's panel , and seen an EOL shorted to the return wires (unlike mines). Considering this is his circuit, how can I identify what and where is faulty in my OP?

Sir i do need your help.


Last edited by Melvin_Melvins; 04/22/14 07:24 AM. Reason: added something important.
Joined: Apr 2014
Posts: 4
New Member
Where should I measure the Vdc sir?

Joined: Jun 2004
Posts: 1,273
Alarm systems are so touchy and the standard of what is acceptable wiring is so high that it's all together different than power wiring or conventional desk top electronics repair.

It can't be learned from a book or video tape.

Too many pitfalls, it's rather like learning to hunt polar bears via a correspondence course.

To top that off, there's enough differences between manufacturers to lead you right off a cliff. Older systems (pre-digital) worked on a fundamentally different design. (detection circuit logic)

Lastly, you CAN'T use a prior installation -- another building -- as a sure fire example to follow. (!!!)

During the last twenty-years alarm technology has changed A LOT. Consequently there is no substitute for highly skilled veteran talent.

I'm not exaggerating when I state that you can spend 1,000 hours to figure out what an expert can solve in one hour.


Fire alarm circuits are UNIQUELY designed to be balanced on a razor's edge. They stay quiet and 'happy' only if absolutely nothing is awry. If ANYTHING, ANYWHERE is off kilter the system goes into 'Trouble Fault.' If the error is of a certain type, the system goes into 'Full Alarm.'

By design, no system will re-set and 'clear' until every last itch is scratched. I've seen four man crews spend five days at 16 hours per day cleaning up circuit faults -- at the same time the manufacturer's tech rep was curing things back at the panel! (Yes, I got tired; I saved my employer from bankruptcy, though.)

Quite simply, you're in way over your head. Place a phone call and get an established firm on the problem.

Fire alarms are tough on the experts -- hopeless for the new guy.

Joined: Nov 2005
Posts: 827
I didn't chime in before because I'm not familiar with the panel you mention. I have made many repairs to Pyrotronics System 3, 35, XL3, and MXL systems though. I've also removed several problems installed by licensed and certified contractors. I recently cleared 300 troubles from an MXL that had every addressible device on loop 2 destroyed. (MSI-10 & 20 pull stations, Tri-B6M, Tri-D, Tri-R modules) Replacement cost of the various modules was upwards of $7200. Their intelligent modules are extremely prone to failure! I had 3 different CSM modules in trouble and Ground Fault Plus and Minus. Here's how I troubleshoot them:
Ground faults are a little tricky because they steer more than one zone. I always measure each zone and look for + or - outputs that are closest to zero volts with respect to ground, and try lifting those first. When all ground faults are cleared, the + and - to ground should be fairly balanced.
The cut sheets for the horn/strobes (A/V) should show the current drawn in alarm mode. The total on a loop should be < the max specified for the signal module, usually 2 to 3 amps. The last A/V should have an EOL resistor attached, ours use 2.2Kohms. Some zones may use PAD panels, which act like repeaters, to drive additional A/Vs, door releases, and the like. They monitor EOLs on each circuit, check the batteries, AC feed, and for ground faults. Any problem in the PAD panel will lift an EOL resistor, to cause a trouble back at the main FACP. One of the professionally installed problems I found was a PAD panel with the inputs and outputs reversed. When the input polarity reversed for what should have been an alarm, the outputs switched to the extremely current limited EOL monitoring Normal mode. The + & - on the boards, tend to refer to the polarity while in alarm so be alert for that.
You should be able to find a cut sheet for your A/Vs. You can drive them through an ammeter with an appropriate DC supply. One polarity should show little to zero current, while reversing should cause horns and strobes and draw no more current than shown on the cut sheet. You should also check for circuit breakers located on signal modules.

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