Jreigner;
I'm not sure exactly what you are trying to say/state in your posts as you mix an eclectic bag of facts into them. I would like to address some of your comments though in order to clarify some needed explanations to our forum members.
Jreigner said:
On a normally closed circuit the EOL has no exact placement- it is not for finding faults. If a circuit breaks on a normally closed circuit (series circuit) which is the beginning and which is the end?
I believe you are getting hung up on series circuit theory and not considering how the
placement of the EOL resistor contributes to circuit performance.
Consider the drawing below attached to this response.
The first scenario shows a typical security contact (shown as a simple contact) with an EOL resistor in series with the control panel. The resistor enables a specific current to flow through this series circuit, thus creating a voltage between the panel's two 'terminals' whose values should be between 4 to 8 volts. This voltage value will depend on the value of the resistor. Note that this resistor is placed at the security panel.
In the second scenario, when the circuit opens (the security contact has the magnet move away from the sensor via a door or window opening) the voltage across the panel's contacts will jump to its maximum, or above 8 volts, thus causing a non-secured state. It does
not matter where the EOL resistor is installed in the 'series' circuit to achieve this result.
In the third scenario, the circuit has the EOL resistor installed in the panel and the security contact is 'closed', but now a nail is driven into the cable (say halfway in the cable run). The security panel will
still see between 4 to 8 volts because the short caused by the nail is in effect, the same short originally caused by the security contact!
In the fourth scenario the EOL resistor is installed at the security contact and now, when a nail is driven into the cable, a 'trouble' event is sensed by the panel as the voltage between its terminals is below 4 volts (actually, near zero). The voltage zone that was impressed across the security panel's terminals by the resistor is removed due to the fact that you caused a short
between that resistor and the panel.
This is the main advantage of an EOL resistor in a
typical security zone! It will also detect if someone tries to thwart the system by obtaining access to the cable and “shorting†the two conductors together (same scenario as the nail shorting them).
Also note that an alarm panel measures and reacts to
voltage impressed on its zoned terminals. The panel does not need to be armed to detect this trouble condition.
Jreigner said:
The resistor must be placed appropriately to supervise the circuit in a way it can’t be defeated or circumvented. Is the resistor at the end of the contact in a public environment the place to put it or maybe will it still supervise the series circuit tucked nicely back in the control panel?
The
only place to properly supervise a typical security contact is to have the EOL resistor mounted at the
end of the line, near the security contact as shown in the attached drawing.
Jreigner said:
Don’t forget burg zones are only armed when needed (except for day zones I know) and can be shunted very easily.†So my question is what is the point of a disable EOL feature in a panel? Is it the I give up mode? This is where think from.
I’m not exactly sure what you are trying to say here. A security zone should see the troubled state without being armed. An EOL resistor can't be easily defeated if mounted near the security contact, or better yet, if you want the advantages of an EOL resistor, obtain a security contact with that feature integrated inside it.
Jreigner said:
So my question is what is the point of a disable EOL feature in a panel? Is it the I give up mode? This is where think from.
In a typical
residential security application, a user might want to elect not to use an EOL resistor for a
SECURITY ZONE (note that I did not state for fire/smoke applications. Those installations must be strictly installed per the manufacturer's instructions, including polarity reversing relays as required)!
The reason is the user is not worried about the limited supervision an EOL resistor offers (if placed near the security contact, it will only detect a short between the contact and the panel). Also, the user is not worried about an attempt to thwart the security system by obtaining access to the cable run and shorting it out (thus being able to open the security contact without the panel detecting the change in voltage).
In my case, I do not use EOL resistors as I know the exact placement of the cable runs in my home (extensive pictures and video of the home’s interior walls before drywall was installed) and I prefer to have the increased noise immunity obtained without using them (the secure/non-secure states are near zero and near 12 volts rather than the three state voltage scenario caused by the EOL resistor in the line).
If someone wants to drill/saw/cut through my stucco walls to thwart a zone by accessing the cable, well good luck in not opening that cable by hacking through it while doing so.
Jreigner said:
Deal with facts -resistance, voltage and current- its what its all about
I could not agree more with this statement!
Regards,
BSR
