diff --git a/Pelco/D.cs b/Pelco/D.cs
index 409e45cf..e60d27ea 100644
--- a/Pelco/D.cs
+++ b/Pelco/D.cs
@@ -121,7 +121,7 @@ public byte[] RemoteReset(uint deviceAddress)
 
         public byte[] Zone(uint deviceAddress, byte zone, Action action)
         {
-            if ((zone < 0x01) & (zone > 0x08))
+            if ((zone < 0x01) || (zone > 0x08))
                 throw new Exception("Zone should be between 0x01 and 0x08");
             var mAction = action == Action.Start ? (byte) 0x11 : (byte) 0x13;
 
@@ -169,7 +169,7 @@ public struct Message
 
             public static byte[] GetMessage(uint address, byte command1, byte command2, byte data1, byte data2)
             {
-                if ((address < 1) & (address > 256))
+                if ((address < 1) || (address > 256))
                     throw new Exception("Pelco D protocol supports 256 devices only");
 
                 Address = byte.Parse(address.ToString(CultureInfo.InvariantCulture));
diff --git a/Pelco/P.cs b/Pelco/P.cs
index d9b09b64..b8719009 100644
--- a/Pelco/P.cs
+++ b/Pelco/P.cs
@@ -121,7 +121,7 @@ public byte[] RemoteReset(uint deviceAddress)
 
         public byte[] Zone(uint deviceAddress, byte zone, Action action)
         {
-            if ((zone < 0x01) & (zone > 0x08))
+            if ((zone < 0x01) || (zone > 0x08))
                 throw new Exception("Zone value should be between 0x01 and 0x08 include");
             byte mAction;
             if (action == Action.Start)