I made a minor change to one file in the c172p that accommodates a

feature I added to the navcom-kx155.xml and the dme.xml in the
Instruments folder.  I wanted to leave the frequencies, etc. on these
dark until there was voltage applied to
/systems/electrical/outputs/nav.  This was accomplished by adding a
param and property alias  pointing to the appropriate value.  Since the
c172p "always" applies 28 volts, this made no change in the c172p, but
allowed me to model the avionics master and battery master realisticly
in pa24-electrical.nas.  I put in comments explaining this at the change
points.

There is a useful  "help > aircraft help" that walks you through the
start procedure and lists the key bindings as well as the key to "light
up" the hot spots.

Aircraft/Instruments-3d/vor/vor.ac

@@ -1,8 +1,9 @@
 AC3Db
 MATERIAL "ac3dmat1" rgb 1 1 1  amb 0.2 0.2 0.2  emis 0 0 0  spec 0 0 0  shi 10  trans 0
+MATERIAL "ac3dmat12" rgb 0.267 0.267 0.267  amb 0.2 0.2 0.2  emis 0 0 0  spec 0.302 0.302 0.302  shi 10  trans 0
 MATERIAL "DefaultWhite" rgb 1 1 1  amb 1 1 1  emis 0.15 0.15 0.15  spec 0.5 0.5 0.5  shi 64  trans 0
 OBJECT world
-kids 8
+kids 9
 OBJECT poly
 name "GlidescopeNeedle"
 crease 45.000000
@@ -15,14 +16,14 @@ numvert 6
 -0.003005 0.000533 0.029784
 numsurf 2
 SURF 0x0
-mat 1
+mat 2
 refs 4
 0 0 0
 3 0 0
 4 0 0
 2 0 0
 SURF 0x0
-mat 1
+mat 2
 refs 4
 0 0 0
 2 0 0
@@ -41,14 +42,14 @@ numvert 6
 -0.003005 0.004974 -0.000532
 numsurf 2
 SURF 0x0
-mat 1
+mat 2
 refs 4
 0 0 0
 2 0 0
 5 0 0
 4 0 0
 SURF 0x0
-mat 1
+mat 2
 refs 4
 1 0 0
 4 0 0
@@ -68,14 +69,14 @@ numvert 6
 -0.004518 0 -0.04
 numsurf 2
 SURF 0x0
-mat 1
+mat 2
 refs 4
 0 0.966797 0.958984
 3 0.00976562 0.958984
 4 0.00976562 0.480469
 5 0.966797 0.480469
 SURF 0x0
-mat 1
+mat 2
 refs 4
 1 0.966797 0
 5 0.966797 0.480469
@@ -95,14 +96,14 @@ numvert 6
 -0.001596 0 -0.04
 numsurf 2
 SURF 0x0
-mat 1
+mat 2
 refs 4
 0 0.998047 1
 3 0 1
 4 0 0.5
 5 0.998047 0.5
 SURF 0x0
-mat 1
+mat 2
 refs 4
 1 0.998047 0
 5 0.998047 0.5
@@ -122,14 +123,14 @@ numvert 6
 0 0 -0.04
 numsurf 2
 SURF 0x0
-mat 1
+mat 2
 refs 4
 0 0.998047 1
 3 0 1
 4 0 0.5
 5 0.998047 0.5
 SURF 0x0
-mat 1
+mat 2
 refs 4
 1 0.998047 0
 5 0.998047 0.5
@@ -193,3 +194,201 @@ refs 4
 1 0.150411 0.0462088
 0 0.65189 0.0462088
 kids 0
+OBJECT poly
+name "disk"
+loc 0 -0.0308515 0.0268345
+crease 101.000000
+numvert 20
+0.01 0.00396059 0.00479285
+0.01 0.00606797 0.00108645
+0.01 0.00533608 -0.00312831
+0.01 0.00210739 -0.0058793
+0.01 -0.00210737 -0.0058793
+0.01 -0.00533607 -0.00312831
+0.01 -0.00606796 0.00108645
+0.01 9.31323e-09 0.00625662
+0.01 -0.00396058 0.00479285
+0 0 0.00625662
+0 0.00396058 0.00479285
+0 0.00606796 0.00108645
+0 0.00533608 -0.00312831
+0 0.00210739 -0.0058793
+0 -0.00210738 -0.0058793
+0 -0.00533607 -0.00312831
+0 -0.00606796 0.00108645
+0 -0.00396058 0.00479285
+0 0 0
+0.01 9.31323e-09 0
+numsurf 27
+SURF 0x10
+mat 1
+refs 3
+19 0.484454 0.5
+0 0.879385 0.826352
+7 1 0.5
+SURF 0x10
+mat 1
+refs 3
+19 0.484454 0.5
+1 0.573978 1
+0 0.879385 0.826352
+SURF 0x10
+mat 1
+refs 3
+19 0.484454 0.5
+2 0.226682 0.939693
+1 0.573978 1
+SURF 0x10
+mat 1
+refs 3
+19 0.484454 0.5
+3 0 0.673648
+2 0.226682 0.939693
+SURF 0x10
+mat 1
+refs 3
+19 0.484454 0.5
+4 0 0.326352
+3 0 0.673648
+SURF 0x10
+mat 1
+refs 3
+19 0.484454 0.5
+5 0.226682 0.0603074
+4 0 0.326352
+SURF 0x10
+mat 1
+refs 3
+19 0.484454 0.5
+6 0.573978 0
+5 0.226682 0.0603074
+SURF 0x10
+mat 1
+refs 3
+19 0.484454 0.5
+8 0.879385 0.173648
+6 0.573978 0
+SURF 0x10
+mat 1
+refs 3
+19 0.484454 0.5
+7 1 0.5
+8 0.879385 0.173648
+SURF 0x10
+mat 1
+refs 4
+7 0 0
+0 0 0
+10 0 0
+9 0 0
+SURF 0x10
+mat 1
+refs 4
+0 0 0
+1 0 0
+11 0 0
+10 0 0
+SURF 0x10
+mat 1
+refs 4
+1 0 0
+2 0 0
+12 0 0
+11 0 0
+SURF 0x10
+mat 1
+refs 4
+2 0 0
+3 0 0
+13 0 0
+12 0 0
+SURF 0x10
+mat 1
+refs 4
+3 0 0
+4 0 0
+14 0 0
+13 0 0
+SURF 0x10
+mat 1
+refs 4
+4 0 0
+5 0 0
+15 0 0
+14 0 0
+SURF 0x10
+mat 1
+refs 4
+5 0 0
+6 0 0
+16 0 0
+15 0 0
+SURF 0x10
+mat 1
+refs 4
+6 0 0
+8 0 0
+17 0 0
+16 0 0
+SURF 0x10
+mat 1
+refs 4
+8 0 0
+7 0 0
+9 0 0
+17 0 0
+SURF 0x10
+mat 1
+refs 3
+18 0.484454 0.5
+10 0.879385 0.826352
+9 1 0.5
+SURF 0x10
+mat 1
+refs 3
+18 0.484454 0.5
+11 0.573978 1
+10 0.879385 0.826352
+SURF 0x10
+mat 1
+refs 3
+18 0.484454 0.5
+12 0.226682 0.939693
+11 0.573978 1
+SURF 0x10
+mat 1
+refs 3
+18 0.484454 0.5
+13 0 0.673648
+12 0.226682 0.939693
+SURF 0x10
+mat 1
+refs 3
+18 0.484454 0.5
+14 0 0.326352
+13 0 0.673648
+SURF 0x10
+mat 1
+refs 3
+18 0.484454 0.5
+15 0.226682 0.0603074
+14 0 0.326352
+SURF 0x10
+mat 1
+refs 3
+18 0.484454 0.5
+16 0.573978 0
+15 0.226682 0.0603074
+SURF 0x10
+mat 1
+refs 3
+18 0.484454 0.5
+17 0.879385 0.173648
+16 0.573978 0
+SURF 0x10
+mat 1
+refs 3
+18 0.484454 0.5
+9 1 0.5
+17 0.879385 0.173648
+kids 0

Aircraft/Instruments/dme.xml

@@ -1,4 +1,4 @@
-<?xml version="1.0"?>
+<?xml version="1.01"?>
 
 <!--
 Default DME instrument.
@@ -22,7 +22,14 @@ click.  Actions always modify the values of properties, either by
 adjusting them, toggling them, or swaping them with other
 properties' values.
 -->
-
+<!--
+Dave Perry added a check for dme voltage greater than 8.0 volts so
+that the dme text does not light up if there is no power supplied.
+This allows more realistic implementation of master switches or
+avionics master switches as is done in pa24-electrical.nas.  This
+change has no affect on the c172p since this voltage is 28 volts
+all the time in that electrical system.
+-->
 <PropertyList>
  <name>DME</name>
  <w-base>128</w-base>
@@ -59,9 +66,15 @@ properties' values.
 
    <layer>
     <condition>
-     <not>
+     <and>
-      <property>/instrumentation/dme/in-range</property>
+      <greater-than>
-     </not>
+       <property>/systems/electrical/outputs/dme</property>
+       <value>8.0</value>
+      </greater-than>
+      <not>
+       <property>/instrumentation/dme/in-range</property>
+      </not>
+     </and>
     </condition>
     <name>display</name>
     <type>text</type>
@@ -81,13 +94,19 @@ properties' values.
    </layer>
 
    <layer>
-    <condition>
-     <greater-than>
-      <property>/instrumentation/dme/indicated-distance-nm</property>
-      <value type="double">999.99</value>
-     </greater-than>
-    </condition>
     <name>display</name>
+    <condition>
+     <and>
+      <greater-than>
+       <property>/systems/electrical/outputs/dme</property>
+       <value>8.0</value>
+      </greater-than>
+      <greater-than>
+       <property>/instrumentation/dme/indicated-distance-nm</property>
+       <value type="double">999.99</value>
+      </greater-than>
+     </and>
+    </condition>
     <type>text</type>
     <font>led</font>
     <point-size>6</point-size>
@@ -106,6 +125,12 @@ properties' values.
 
    <layer>
     <name>display</name>
+     <condition>
+      <greater-than>
+       <property>/systems/electrical/outputs/dme</property>
+       <value>8.0</value>
+      </greater-than>
+     </condition>
     <type>text</type>
     <font>led</font>
     <point-size>6</point-size>
@@ -136,6 +161,12 @@ properties' values.
 
   <layer>
    <name>ground speed towards station</name>
+     <condition>
+      <greater-than>
+       <property>/systems/electrical/outputs/dme</property>
+       <value>8.0</value>
+      </greater-than>
+     </condition>
    <type>switch</type>
 
    <layer>
@@ -150,9 +181,15 @@ properties' values.
 
    <layer>
     <condition>
-     <not>
+     <and>
+      <greater-than>
+       <property>/systems/electrical/outputs/dme</property>
+       <value>8.0</value>
+      </greater-than>
+      <not>
        <property>/instrumentation/dme/in-range</property>
-     </not>
+      </not>
+     </and>
     </condition>
     <name>display</name>
     <type>text</type>
@@ -173,10 +210,16 @@ properties' values.
 
    <layer>
     <condition>
+     <and>
+      <greater-than>
+       <property>/systems/electrical/outputs/dme</property>
+       <value>8.0</value>
+      </greater-than>
      <greater-than>
        <property>/instrumentation/dme/indicated-ground-speed-kt</property>
        <value type="double">999</value>
      </greater-than>
+     </and>
     </condition>
     <name>display</name>
     <type>text</type>
@@ -196,6 +239,12 @@ properties' values.
    </layer>
 
    <layer>
+     <condition>
+      <greater-than>
+       <property>/systems/electrical/outputs/dme</property>
+       <value>8.0</value>
+      </greater-than>
+     </condition>
     <type>text</type>
     <font>led</font>
     <point-size>6</point-size>
@@ -237,9 +286,15 @@ properties' values.
 
    <layer>
     <condition>
+     <and>
+      <greater-than>
+       <property>/systems/electrical/outputs/dme</property>
+       <value>8.0</value>
+      </greater-than>
      <not>
       <property>/instrumentation/dme/in-range</property>
      </not>
+    </and>
     </condition>
     <name>display</name>
     <type>text</type>
@@ -260,10 +315,16 @@ properties' values.
 
    <layer>
     <condition>
+     <and>
+      <greater-than>
+       <property>/systems/electrical/outputs/dme</property>
+       <value>8.0</value>
+      </greater-than>
      <greater-than>
       <property>/instrumentation/dme/indicated-time-min</property>
       <value type="double">99</value>
      </greater-than>
+     </and>
     </condition>
     <name>display</name>
     <type>text</type>
@@ -283,6 +344,12 @@ properties' values.
    </layer>
 
    <layer>
+     <condition>
+      <greater-than>
+       <property>/systems/electrical/outputs/dme</property>
+       <value>8.0</value>
+      </greater-than>
+     </condition>
     <type>text</type>
     <font>led</font>
     <point-size>6</point-size>

Aircraft/Instruments/navcom-kx155.xml

@@ -24,6 +24,19 @@ adjusting them, toggling them, or swaping them with other
 properties' values.
 -->
 
+<!--
+2/10/06
+Dave Perry added a check for Nav/Com power, so the frequencies won't 
+light if
+/systems/electrical/outputs/nav is less than 8.0 volts. See the con-
+dition added for these text layers below. This allows a more realistic 
+master switch and avionics master switch implementation in the electrical 
+system model.  I also checked to make sure this does not negatively 
+impact the c172p. Had to add a property alias to the params after the 
+nav1.xml include in c172p-2d-panel.xml. Since the electrical system 
+for the c172p has this voltage at 28 volts, these changes have no 
+impact on the c172p.
+-->
 <PropertyList>
  
  <name>NavCom Radio</name>
@@ -37,6 +50,7 @@ properties' values.
   <nav-freq-standby-prop>/instrumentation/nav[0]/frequencies/standby-mhz</nav-freq-standby-prop>
   <nav-morse-id-volume-prop>/instrumentation/nav[0]/volume</nav-morse-id-volume-prop>
   <nav-morse-ident-toggle-prop>/instrumentation/nav[0]/ident</nav-morse-ident-toggle-prop>
+  <nav-com-pwr-volts-prop>/systems/electrical/outputs/nav[0]</nav-com-pwr-volts-prop>
  </params>
 
  <layers>
@@ -54,6 +68,12 @@ properties' values.
 
   <layer>
    <name>nav frequencies</name>
+   <condition>
+    <greater-than>
+     <property alias="../../../../../params/nav-com-pwr-volts-prop"/>
+     <value>8.0</value>
+    </greater-than>
+   </condition>
    <type>text</type>
    <font>led</font>
    <point-size>6.5</point-size>
@@ -88,6 +108,12 @@ properties' values.
 
   <layer>
    <name>com frequencies</name>
+   <condition>
+    <greater-than>
+     <property alias="../../../../../params/nav-com-pwr-volts-prop"/>
+     <value>8.0</value>
+    </greater-than>
+   </condition>
    <type>text</type>
    <font>led</font>
    <point-size>6.5</point-size>

Aircraft/c172p/Models/c172p-2d-panel.xml

@@ -1,4 +1,4 @@
-<?xml version="1.0"?>
+<?xml version="1.01"?>
 
 <!--
 Legacy 2D instruments and actions for the 3D C172P cockpit.
@@ -202,6 +202,14 @@ Legacy 2D instruments and actions for the 3D C172P cockpit.
    <nav-heading-needle-deflection>/instrumentation/nav[1]/heading-needle-deflection</nav-heading-needle-deflection>
     <nav-has-gs-needle>/sim/instrument-options/nav[1]/has-gs-needle</nav-has-gs-needle>
     <nav-needles-pivot>/sim/instrument-options/nav[1]/needles-pivot</nav-needles-pivot>
+<!--  Dave Perry added a check for nav voltage in Aircraft/Instruments/navcom-kx155.xml
+which won't "light up" the radio frequencies if this voltage is less than 8.0 volts.
+This allows more realistic implementation of a master switch or an avionics master
+switch, as is done in pa24-electrical.nas.  Since the c172p has this voltage at 28 volts,
+this change has no affect on the c172p. The following param is required for this to
+work.
+--> 
+    <nav-com-pwr-volts-prop>/systems/electrical/outputs/nav[1]</nav-com-pwr-volts-prop>
   </params>
   <x>620</x>
   <y>100</y>