Please Explain Vista 20P Wiring Diagram

[jtw]

Hi All!
 
What is the zone 4 drawing on this diagram supposed to represent?  There is nothing on the 20p in our house that appears to be wired like this.  http://www.myalarmguy.net/h3.html
 
It shows 2 closed switches and 1 open  switch.  They are all in series.  The open switch has a resistor wired in parallel.  Thanks.

 

[SterlingDonnelly]

That picture is just showing a generic closed loop with a 2k resistor wired in to show which zones go to which terminals on the panel.
 
That picture will not help you idenfiy an unknown zone in your house. Do you have an alphanumeric keypad?

 

[RAL]

The drawing is showing an example of how both normally open and normally closed contacts (switches) can be wired in a single zone with an EOL resistor.
 
The two switches without a resistor are normally closed switches.  With NC switches, the EOL resistor is placed in series.  The switch with a resistor across it is a normally open switch.  With NO switches, the resistor is wired in parallel.
 
How many contacts are wired in a zone and whether they are NC or NO will vary with the installation.  In some installations, there may be only a single contact per zone.  In other cases, all the windows in one room may be wired into a single zone.  Fewer contacts per zone gives you more granularity and makes it easier to tell which door or window is not secure.

 

[jtw]

The two switches without a resistor are normally closed switches.  With NC switches, the EOL resistor is placed in series.  The switch with a resistor across it is a normally open switch.  With NO switches, the resistor is wired in parallel.

OK.  I think I got it.  Let me say this in my own words to see if I have it right.
 
In both of those 2 circuits, a signal, which has been reduced by the resistor, indicates that everything is in the unalarmed state.  
 
For the circuit with 1 normally closed switch and a resistor in series, full signal or no signal is an alarm state.  Full signal indicates a short, and no signal indicates a true alarm, a break in the circuit, or a faulty switch (if the switch is fail open).
 
For the circuit with 1 normally open switch and the resistor in parallel, again, full signal or no signal is an alarm state.  Full signal would indicate a true alarm, a short, or a faulty switch (if the switch is fail closed).  No signal would indicate a break in the circuit.
 
Is this about right?  Does the 20p distinguish between the different failure modes?

 

[RAL]

OK.  I think I got it.  Let me say this in my own words to see if I have it right.
 
In both of those 2 circuits, a signal, which has been reduced by the resistor, indicates that everything is in the unalarmed state.  
 
For the circuit with 1 normally closed switch and a resistor in series, full signal or no signal is an alarm state.  Full signal indicates a short, and no signal indicates a true alarm, a break in the circuit, or a faulty switch (if the switch is fail open).
 
For the circuit with 1 normally open switch and the resistor in parallel, again, full signal or no signal is an alarm state.  Full signal would indicate a true alarm, a short, or a faulty switch (if the switch is fail closed).  No signal would indicate a break in the circuit.
 
Is this about right?  Does the 20p distinguish between the different failure modes?

 
Yes, you understand it correctly.  I'm not enough of an expert on the 20P to say whether it will tell you the details of what it thinks is wrong with a zone, other than to display a "CHECK  xxx" message on the keypad, where xxx is the zone number.

 

[Del91574]

A standard 3 state EOLR setup is NOT going to give you a failure mode of what is going on with a circuit. That said, the Vistas will give you the 4th state of a trouble for a low/high resistance circuit, indicated by CHECK (zone) XX on the KP. That value is going to be +/- 500 ohms of the EOLR value.
 
If you want to monitor the zones for all failure or compromise, you would need to use a DEOLR method (4 state wiring) and that still does not guarantee all the failure methods will be supervised or annunciated clearly.