Is it or isn't it....I recently ran across a test question that said, and I think I remember it exactly:
Where do you put an EOL resistor on a circuit that uses NO sensors.
in series at the panel in parallel at the panel in series at the last sensor in parallel at the last sensor
There is no series/parallel here...just put the resistor across the two circuit screws and that's it. I know my electronics, but this one is making my head hurt. It could be a bad question, one that some goof wrote and didn't get reviewed properly.
In most cases the answer should be in parallel at the last sensor. However that assumes that you will generate a trouble on open and alarm on short. If you were trying to be too clever by half, you could program certain panels to have the alarm triggers reversed and wire it a number of funny ways. You would be shot on site by the next technician that serviced the account however. Some panels use zone doubling that can be equally as irritating to service if done incorrectly.
Sensors are wired in parallel and the EOL goes in parallel with last sensor.
If you were to put it at the panel end by mistake then cutting the wire has no effect.
This is how it works...
With sensors open the impedance = EOL ohms = normal status With sensors closed = 0 ohms = Alarm With wire cut = Open circuit/High ohms = Tamper With wire shorted = 0 ohms = Alarm (tamper)
Single Pole Normally Open Single Pole Normally Closed Double Pole Normally Open Double Pole Normally Closed etc. etc.
When energized the relay contacts will change state to the opposite of what it was at rest.
In industrial wiring you have switches that are either of the following.
Normally Closed
Normally Open
Normally Open Held Closed
Normally Closed Held Open
In the alarm industry it is thought of as an OPEN Loop or a CLOSED Loop.
Wiring colors for an electrician is mostly Black is Hot, White is Neutral and Green is Ground. Any other color is considered to be Hot.
The phone guy uses Green for TIP and RED for Ring unless it is twisted pair then it is White w/ Blue strip as TIP and Blue w/ White strip as Ring for the first pair and then on Orange, Green, Brown, Slate to ID the other colors.
Alarm guys us RED as Positive and Black as Negative for power unless it is a current limiting circuit for a zone then it can be many other things. Generally is it Red/Black for first pair, Green/White for second pair, Blue/Brown for third pair, Yellow/Orange for the forth pair................................ then I start to lose my brain...............................
THEN you have the guy that thought he was a homebrew electrician that is now doing alarms and only buys telephone station wire for all his jobs because it is very cheap.
He ends up using Black for positive and Yellow for negative and the Red and Green for the motion zone loop.
If you have worked in multi-professions it can all be rather mind-bending. REALLY!!!!
They are coming to take me away Ha Ha Ha Hee Hee Hee............................................
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