diff --git a/S7.Net/Protocol/ConnectionRequest.cs b/S7.Net/Protocol/ConnectionRequest.cs
index 9c6c5bb..19b441c 100644
--- a/S7.Net/Protocol/ConnectionRequest.cs
+++ b/S7.Net/Protocol/ConnectionRequest.cs
@@ -6,7 +6,7 @@ namespace S7.Net.Protocol
     {
         public static byte[] GetCOTPConnectionRequest(CpuType cpu, Int16 rack, Int16 slot)
         {
-            var tsapPair = GetDefaultTsapPair(cpu, rack, slot);
+            var tsapPair = TsapPair.GetDefaultTsapPair(cpu, rack, slot);
 
             byte[] bSend1 = {
                     3, 0, 0, 22, //TPKT
@@ -28,56 +28,5 @@ namespace S7.Net.Protocol
 
             return bSend1;
         }
-
-        /// <summary>
-        /// Builds a <see cref="TsapPair" /> that can be used to connect to a PLC using the default connection
-        /// addresses.
-        /// </summary>
-        /// <remarks>
-        /// The remote TSAP is constructed using <code>new Tsap(0x03, (byte) ((rack &lt;&lt; 5) | slot))</code>.
-        /// </remarks>
-        /// <param name="cpuType">The CPU type of the PLC.</param>
-        /// <param name="rack">The rack of the PLC's network card.</param>
-        /// <param name="slot">The slot of the PLC's network card.</param>
-        /// <returns>A TSAP pair that matches the given parameters.</returns>
-        /// <exception cref="ArgumentOutOfRangeException">The <paramref name="cpuType"/> is invalid.
-        ///
-        /// -or-
-        ///
-        /// The <paramref name="rack"/> parameter is greater than 15.
-        ///
-        /// -or-
-        ///
-        /// The <paramref name="slot"/> parameter is greater than 15.</exception>
-        public static TsapPair GetDefaultTsapPair(CpuType cpuType, int rack, int slot)
-        {
-            if (rack > 0x0F) throw InvalidRackOrSlot(rack, nameof(rack));
-            if (slot > 0x0F) throw InvalidRackOrSlot(slot, nameof(slot));
-
-            switch (cpuType)
-            {
-                case CpuType.S7200:
-                    return new TsapPair(new Tsap(0x10, 0x00), new Tsap(0x10, 0x00));
-                case CpuType.Logo0BA8:
-                    // The actual values are probably on a per-project basis
-                    return new TsapPair(new Tsap(0x01, 0x00), new Tsap(0x01, 0x02));
-                case CpuType.S7200Smart:
-                case CpuType.S71200:
-                case CpuType.S71500:
-                case CpuType.S7300:
-                case CpuType.S7400:
-                    // Testing with S7 1500 shows only the remote TSAP needs to match. This might differ for other
-                    // PLC types.
-                    return new TsapPair(new Tsap(0x01, 0x00), new Tsap(0x03, (byte) ((rack << 5) | slot)));
-                default:
-                    throw new ArgumentOutOfRangeException(nameof(cpuType), "Invalid CPU Type specified");
-            }
-        }
-
-        private static ArgumentOutOfRangeException InvalidRackOrSlot(int value, string name)
-        {
-            return new ArgumentOutOfRangeException(name,
-                $"Invalid {name} value specified (decimal: {value}, hexadecimal: {value:X}), maximum value is 15 (decimal) or 0x0F (hexadecimal).");
-        }
     }
 }
diff --git a/S7.Net/Protocol/TsapPair.cs b/S7.Net/Protocol/TsapPair.cs
index 0869b23..4a329d3 100644
--- a/S7.Net/Protocol/TsapPair.cs
+++ b/S7.Net/Protocol/TsapPair.cs
@@ -1,4 +1,6 @@
-namespace S7.Net.Protocol
+using System;
+
+namespace S7.Net.Protocol
 {
     /// <summary>
     /// Implements a pair of TSAP addresses used to connect to a PLC.
@@ -26,5 +28,69 @@
             Local = local;
             Remote = remote;
         }
+
+        /// <summary>
+        /// Builds a <see cref="TsapPair" /> that can be used to connect to a PLC using the default connection
+        /// addresses.
+        /// </summary>
+        /// <remarks>
+        /// The remote TSAP is constructed using <code>new Tsap(0x03, (byte) ((rack &lt;&lt; 5) | slot))</code>.
+        /// </remarks>
+        /// <param name="cpuType">The CPU type of the PLC.</param>
+        /// <param name="rack">The rack of the PLC's network card.</param>
+        /// <param name="slot">The slot of the PLC's network card.</param>
+        /// <returns>A TSAP pair that matches the given parameters.</returns>
+        /// <exception cref="ArgumentOutOfRangeException">The <paramref name="cpuType"/> is invalid.
+        ///
+        /// -or-
+        ///
+        /// The <paramref name="rack"/> parameter is less than 0.
+        ///
+        /// -or-
+        ///
+        /// The <paramref name="rack"/> parameter is greater than 15.
+        ///
+        /// -or-
+        ///
+        /// The <paramref name="slot"/> parameter is less than 0.
+        ///
+        /// -or-
+        ///
+        /// The <paramref name="slot"/> parameter is greater than 15.</exception>
+        public static TsapPair GetDefaultTsapPair(CpuType cpuType, int rack, int slot)
+        {
+            if (rack < 0) throw InvalidRackOrSlot(rack, nameof(rack), "minimum", 0);
+            if (rack > 0x0F) throw InvalidRackOrSlot(rack, nameof(rack), "maximum", 0x0F);
+
+            if (slot < 0) throw InvalidRackOrSlot(slot, nameof(slot), "minimum", 0);
+            if (slot > 0x0F) throw InvalidRackOrSlot(slot, nameof(slot), "maximum", 0x0F);
+
+            switch (cpuType)
+            {
+                case CpuType.S7200:
+                    return new TsapPair(new Tsap(0x10, 0x00), new Tsap(0x10, 0x00));
+                case CpuType.Logo0BA8:
+                    // The actual values are probably on a per-project basis
+                    return new TsapPair(new Tsap(0x01, 0x00), new Tsap(0x01, 0x02));
+                case CpuType.S7200Smart:
+                case CpuType.S71200:
+                case CpuType.S71500:
+                case CpuType.S7300:
+                case CpuType.S7400:
+                    // Testing with S7 1500 shows only the remote TSAP needs to match. This might differ for other
+                    // PLC types.
+                    return new TsapPair(new Tsap(0x01, 0x00), new Tsap(0x03, (byte) ((rack << 5) | slot)));
+                default:
+                    throw new ArgumentOutOfRangeException(nameof(cpuType), "Invalid CPU Type specified");
+            }
+        }
+
+        private static ArgumentOutOfRangeException InvalidRackOrSlot(int value, string name, string extrema,
+            int extremaValue)
+        {
+            return new ArgumentOutOfRangeException(name,
+                $"Invalid {name} value specified (decimal: {value}, hexadecimal: {value:X}), {extrema} value " +
+                $"is {extremaValue} (decimal) or {extremaValue:X} (hexadecimal).");
+        }
     }
 }
\ No newline at end of file