diff --git a/DbToDevicePlanning.cs b/DbToDevicePlanning.cs
new file mode 100644
index 0000000..a4589f5
--- /dev/null
+++ b/DbToDevicePlanning.cs
@@ -0,0 +1,88 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace HanvonF710XAttendanceService
+{
+    /// <summary>
+    /// Pure planning logic for DB_TO_DEVICE jobs (testable without device/DB I/O).
+    /// </summary>
+    internal static class DbToDevicePlanning
+    {
+        public const int TemplateLoadBatchSize = 50;
+
+        public static bool ShouldIgnoreSourceDevice(TemplateTransferMode mode)
+        {
+            return mode == TemplateTransferMode.DB_TO_DEVICE;
+        }
+
+        public static List<string> NormalizeEmployeeIds(IEnumerable<string> employeeIds)
+        {
+            if (employeeIds == null)
+            {
+                return new List<string>();
+            }
+
+            return employeeIds
+                .Where(id => !string.IsNullOrWhiteSpace(id))
+                .Select(id => id.Trim())
+                .Distinct(StringComparer.OrdinalIgnoreCase)
+                .ToList();
+        }
+
+        /// <summary>
+        /// Resolves which employee serial numbers should be synced from HRMS DB to target devices.
+        /// </summary>
+        public static List<string> ResolveEmployeeIds(
+            TemplateTransferJob job,
+            Func<IReadOnlyList<string>, List<string>> loadByDepartmentIds,
+            Func<List<string>> loadRegisteredOnTargets)
+        {
+            if (job == null)
+            {
+                return new List<string>();
+            }
+
+            if (job.EmpIds != null && job.EmpIds.Count > 0)
+            {
+                return NormalizeEmployeeIds(job.EmpIds);
+            }
+
+            if (job.DepartmentIds != null && job.DepartmentIds.Count > 0)
+            {
+                if (loadByDepartmentIds != null)
+                {
+                    var fromDepartments = loadByDepartmentIds(job.DepartmentIds);
+                    if (fromDepartments != null && fromDepartments.Count > 0)
+                    {
+                        return NormalizeEmployeeIds(fromDepartments);
+                    }
+                }
+            }
+
+            return NormalizeEmployeeIds(loadRegisteredOnTargets != null ? loadRegisteredOnTargets() : null);
+        }
+
+        public static int ComputeTemplateLoadBatchCount(int employeeCount)
+        {
+            if (employeeCount <= 0)
+            {
+                return 0;
+            }
+
+            return (employeeCount + TemplateLoadBatchSize - 1) / TemplateLoadBatchSize;
+        }
+
+        public static int ComputeLastTemplateLoadBatchSize(int employeeCount)
+        {
+            if (employeeCount <= 0)
+            {
+                return 0;
+            }
+
+            int remainder = employeeCount % TemplateLoadBatchSize;
+            return remainder == 0 ? TemplateLoadBatchSize : remainder;
+        }
+    }
+}
+
diff --git a/DbToDevicePlanningTests.cs b/DbToDevicePlanningTests.cs
new file mode 100644
index 0000000..2325e1f
--- /dev/null
+++ b/DbToDevicePlanningTests.cs
@@ -0,0 +1,132 @@
+using System;
+using System.Collections.Generic;
+
+namespace HanvonF710XAttendanceService
+{
+    /// <summary>
+    /// Lightweight unit tests for DB_TO_DEVICE planning logic (no MSTest dependency).
+    /// </summary>
+    internal static class DbToDevicePlanningTests
+    {
+        public static int RunAll()
+        {
+            int failed = 0;
+            failed += Run("1 DB_TO_DEVICE ignores source device", TestDbToDeviceIgnoresSource);
+            failed += Run("2 DEVICE_TO_DB requires source device", TestDeviceToDbRequiresSource);
+            failed += Run("3 DB_TO_DEVICE allows empty SourceIp planning", TestDbToDeviceAllowsEmptySourceIp);
+            failed += Run("4 EmpIds only selection", TestEmpIdsFilter);
+            failed += Run("5 DepartmentIds selection", TestDepartmentIdsFallback);
+            failed += Run("6 empty EmpIds uses registered employees", TestEmptyEmpIdsUsesRegistered);
+            failed += Run("7 normalize employee ids", TestNormalizeEmployeeIds);
+            failed += Run("8 DEVICE_TO_DEVICE requires source device", TestDeviceToDeviceRequiresSource);
+            failed += Run("9 template load batches for 673 employees", TestTemplateLoadBatchCount673);
+            return failed;
+        }
+
+        private static int Run(string name, Func<bool> test)
+        {
+            try
+            {
+                if (!test())
+                {
+                    Console.WriteLine("FAIL: " + name);
+                    return 1;
+                }
+                Console.WriteLine("PASS: " + name);
+                return 0;
+            }
+            catch (Exception ex)
+            {
+                Console.WriteLine("FAIL: " + name + " err=" + ex.Message);
+                return 1;
+            }
+        }
+
+        private static bool TestDbToDeviceIgnoresSource()
+        {
+            return DbToDevicePlanning.ShouldIgnoreSourceDevice(TemplateTransferMode.DB_TO_DEVICE);
+        }
+
+        private static bool TestDeviceToDbRequiresSource()
+        {
+            return !DbToDevicePlanning.ShouldIgnoreSourceDevice(TemplateTransferMode.DEVICE_TO_DB);
+        }
+
+        private static bool TestDeviceToDeviceRequiresSource()
+        {
+            return !DbToDevicePlanning.ShouldIgnoreSourceDevice(TemplateTransferMode.DEVICE_TO_DEVICE);
+        }
+
+        private static bool TestDbToDeviceAllowsEmptySourceIp()
+        {
+            var job = new TemplateTransferJob("1", true, "", new List<string> { "192.168.90.223" },
+                new List<string> { "5" }, null);
+            var ids = DbToDevicePlanning.ResolveEmployeeIds(job, _ => new List<string>(), () => new List<string> { "5" });
+            return ids.Count == 1 && ids[0] == "5";
+        }
+
+        private static bool TestOtherModesRequireSource()
+        {
+            return TestDeviceToDbRequiresSource() && TestDeviceToDeviceRequiresSource();
+        }
+
+        private static bool TestEmpIdsFilter()
+        {
+            var job = new TemplateTransferJob("1", true, "10.0.1.3", new List<string> { "192.168.90.223" },
+                new List<string> { "5", "55", "96" }, null);
+
+            var ids = DbToDevicePlanning.ResolveEmployeeIds(
+                job,
+                _ => new List<string> { "999" },
+                () => new List<string> { "999" });
+
+            return ids.Count == 3
+                && ids.Contains("5")
+                && ids.Contains("55")
+                && ids.Contains("96");
+        }
+
+        private static bool TestDepartmentIdsFallback()
+        {
+            var job = new TemplateTransferJob("1", true, "", new List<string> { "192.168.90.223" },
+                null, new List<string> { "10", "20" });
+
+            bool deptCalled = false;
+            var ids = DbToDevicePlanning.ResolveEmployeeIds(
+                job,
+                departmentIds =>
+                {
+                    deptCalled = true;
+                    return new List<string> { "100", "200" };
+                },
+                () => new List<string> { "300" });
+
+            return deptCalled && ids.Count == 2 && ids.Contains("100") && ids.Contains("200");
+        }
+
+        private static bool TestEmptyEmpIdsUsesRegistered()
+        {
+            var job = new TemplateTransferJob("1", true, "", new List<string> { "192.168.90.223" },
+                null, null);
+
+            var ids = DbToDevicePlanning.ResolveEmployeeIds(
+                job,
+                _ => new List<string>(),
+                () => new List<string> { "5", "55" });
+
+            return ids.Count == 2 && ids.Contains("5") && ids.Contains("55");
+        }
+
+        private static bool TestNormalizeEmployeeIds()
+        {
+            var ids = DbToDevicePlanning.NormalizeEmployeeIds(new[] { " 5 ", "5", "", null, "96" });
+            return ids.Count == 2 && ids[0] == "5" && ids[1] == "96";
+        }
+
+        private static bool TestTemplateLoadBatchCount673()
+        {
+            return DbToDevicePlanning.ComputeTemplateLoadBatchCount(673) == 14
+                && DbToDevicePlanning.ComputeLastTemplateLoadBatchSize(673) == 23;
+        }
+    }
+}
diff --git a/DeviceSettingsConfig.cs b/DeviceSettingsConfig.cs
index 7edfbb4..f2cdafe 100644
--- a/DeviceSettingsConfig.cs
+++ b/DeviceSettingsConfig.cs
@@ -97,7 +97,7 @@ namespace HanvonF710XAttendanceService
                         var enabled = TryParseBool((string)jobEl.Attribute("Enabled"), out var jEnabled) && jEnabled;
                         var sourceIp = (string)jobEl.Attribute("SourceIp") ?? (string)jobEl.Attribute("SourceIP") ?? "";
 
-                        if (string.IsNullOrWhiteSpace(id) || string.IsNullOrWhiteSpace(sourceIp))
+                        if (string.IsNullOrWhiteSpace(id))
                         {
                             continue;
                         }
@@ -124,7 +124,20 @@ namespace HanvonF710XAttendanceService
                                 .ToList();
                         }
 
-                        ttConfig.Jobs.Add(new TemplateTransferJob(id.Trim(), enabled, sourceIp.Trim(), targets, empIds));
+                        var departmentIdsAttr = (string)jobEl.Attribute("DepartmentIds")
+                            ?? (string)jobEl.Attribute("DepartmentIDs")
+                            ?? (string)jobEl.Attribute("DeptIds");
+                        List<string> departmentIds = null;
+                        if (!string.IsNullOrWhiteSpace(departmentIdsAttr))
+                        {
+                            departmentIds = departmentIdsAttr
+                                .Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries)
+                                .Select(v => v.Trim())
+                                .Where(v => v.Length > 0)
+                                .ToList();
+                        }
+
+                        ttConfig.Jobs.Add(new TemplateTransferJob(id.Trim(), enabled, sourceIp.Trim(), targets, empIds, departmentIds));
                     }
 
                     parsed.TemplateTransfer = ttConfig;
@@ -188,13 +201,14 @@ namespace HanvonF710XAttendanceService
 
     internal sealed class TemplateTransferJob
     {
-        public TemplateTransferJob(string id, bool enabled, string sourceIp, List<string> targetIps, List<string> empIds)
+        public TemplateTransferJob(string id, bool enabled, string sourceIp, List<string> targetIps, List<string> empIds, List<string> departmentIds = null)
         {
             Id = id ?? "";
             Enabled = enabled;
             SourceIp = sourceIp ?? "";
             TargetIps = targetIps ?? new List<string>();
             EmpIds = empIds ?? new List<string>();
+            DepartmentIds = departmentIds ?? new List<string>();
         }
 
         public string Id { get; }
@@ -202,6 +216,7 @@ namespace HanvonF710XAttendanceService
         public string SourceIp { get; }
         public List<string> TargetIps { get; }
         public List<string> EmpIds { get; }
+        public List<string> DepartmentIds { get; }
     }
 }