diff --git a/DataStreamInterface/DataFrame.cs b/DataStreamInterface/DataFrame.cs
index 6338df650..2f5835223 100644
--- a/DataStreamInterface/DataFrame.cs
+++ b/DataStreamInterface/DataFrame.cs
@@ -7,12 +7,12 @@ namespace DataStreamInterface
 {
     public class DataFrame
     {
-        public readonly UInt64 ID;          /// Frame ID
+        public readonly Int64 ID;          /// Frame ID
         public readonly double Time;        /// Time stamp in units of time
         public readonly double Volume;      /// Volume in units of volume
         public readonly double[] Quantity;  /// An array of optional quantities in their respective units
 
-        public DataFrame(UInt64 id, double time, double volume, double[] quantity)
+        public DataFrame(Int64 id, double time, double volume, double[] quantity)
         {
             ID = id;
             Time = time;
diff --git a/DataStreamInterface/DataStreamInterface.csproj b/DataStreamInterface/DataStreamInterface.csproj
index 49ae9f254..df67cc35b 100644
--- a/DataStreamInterface/DataStreamInterface.csproj
+++ b/DataStreamInterface/DataStreamInterface.csproj
@@ -9,7 +9,7 @@
     <AppDesignerFolder>Properties</AppDesignerFolder>
     <RootNamespace>DataStreamInterface</RootNamespace>
     <AssemblyName>DataStreamInterface</AssemblyName>
-    <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v4.7.2</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
     <TargetFrameworkProfile />
   </PropertyGroup>
@@ -21,6 +21,7 @@
     <DefineConstants>DEBUG;TRACE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
+    <Prefer32Bit>false</Prefer32Bit>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <DebugType>pdbonly</DebugType>
@@ -29,9 +30,11 @@
     <DefineConstants>TRACE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
+    <Prefer32Bit>false</Prefer32Bit>
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />
+    <Reference Include="System.ComponentModel.Composition" />
     <Reference Include="System.Core" />
     <Reference Include="System.Xml.Linq" />
     <Reference Include="System.Data.DataSetExtensions" />
diff --git a/DataStreamInterface/Doc/Software interface for datastream water meters.docx b/DataStreamInterface/Doc/Software interface for datastream water meters.docx
index 09770fbc1..2fdd60f86 100644
Binary files a/DataStreamInterface/Doc/Software interface for datastream water meters.docx and b/DataStreamInterface/Doc/Software interface for datastream water meters.docx differ
diff --git a/DataStreamInterface/IDataStreamMeter.cs b/DataStreamInterface/IDataStreamMeter.cs
index 6255b1b0a..e4868b009 100644
--- a/DataStreamInterface/IDataStreamMeter.cs
+++ b/DataStreamInterface/IDataStreamMeter.cs
@@ -2,58 +2,82 @@
 /// Copyright (c) 2020 Sensus Slovensko a.s.
 ///
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
 
 namespace DataStreamInterface
 {
     public interface IDataStreamMeter
     {
+        /// <summary>
+        /// Returns count of water meters supported by the data stream component
+        /// </summary>
+        /// <returns>Water meters count</returns>
+        int GetMetersCount();
+
         /// <summary>
         /// Get state of the connected data stream meter
         /// </summary>
+        /// <param name="meterIx">Index of the meter in range 0 .. (GetMetersCount() - 1)</param>
         /// <param name="state">Current state of the meter</param>
+        /// <param name="parameter">Current extra parameter of the meter</param>
         /// <returns>true when successful</returns>
-        bool GetState(out int state, out string parameter);
+        bool GetState(int meterIx, out int state, out string parameter);
 
         /// <summary>
         /// Set state of the connected data stream meter
         /// </summary>
+        /// <param name="meterIx">Index of the meter in range 0 .. (GetMetersCount() - 1)</param>
         /// <param name="state">Required state of the meter</param>
+        /// <param name="parameter">Required extra parameter of the meter</param>
         /// <returns>true when successful</returns>
-        bool SetState(int state, string parameter);
+        bool SetState(int meterIx, int state, string parameter);
+
+        bool SetStateAll(int state, string parameter);
 
         /// <summary>
         /// Establish connection with a data stream meter
         /// </summary>
+        /// <param name="meterIx">Index of the meter in range 0 .. (GetMetersCount() - 1)</param>
         /// <param name="connectionParameters">Connection parameters</param>
         /// <param name="meterId">Meter ID (e.g. serial number)</param>
         /// <returns>true when successful</returns>
-        bool OpenConnection(string connectionParameters, out string meterId);
-
-        /// <summary>
-        /// Closes connection with the data stream meter
-        /// </summary>
-        /// <returns>true when successful</returns>
-        bool CloseConnection();
+        bool OpenConnection(int meterIx, string connectionParameters, out string meterId);
 
         /// <summary>
         /// Stars saving measurement results into internal data structures of the component.
         /// Each data frame obtains a unique ID.
         /// The very first data fraim obrains ID = 0.
         /// </summary>
+        /// <param name="meterIx">Index of the meter in range 0 .. (GetMetersCount() - 1)</param>
         /// <returns>true when successful</returns>
-        bool StartMeasurement();
+        bool StartMeasurement(int meterIx);
+
+        bool StartMeasurementAll();
 
         /// <summary>
         /// Stops saving measurement results into internal data structures of the component.
         /// Updates ID of the last date frame received from the meter.
         /// </summary>
-        /// <param name="lastFrameID">ID of the last date frame</param>
+        /// <param name="meterIx">Index of the meter in range 0 .. (GetMetersCount() - 1)</param>
+        /// <param name="storedFramesCount">Number of stored date frames</param>
         /// <returns>true when successful</returns>
-        bool StopMeasurement(out UInt64 lastFrameID);
+        bool StopMeasurement(int meterIx, out Int64 storedFramesCount);
+
+        bool StopMeasurementAll(out Int64[] storedFramesCounts);
+
+        /// <summary>
+        /// Closes connection with the data stream meter
+        /// </summary>
+        /// <param name="meterIx">Index of the meter in range 0 .. (GetMetersCount() - 1)</param>
+        /// <returns>true when successful</returns>
+        bool CloseConnection(int meterIx);
+
+        bool CloseConnectionAll();
+
+        /// <summary>
+        /// This function is called when TBF program is shutting down.
+        /// </summary>
+        /// <returns>true when successful</returns>
+        bool Shutdown();
 
         ///------------------------------------------------
         /// Units of time, volume and optional quantities
@@ -70,7 +94,7 @@ namespace DataStreamInterface
         Unit GetVolumeUnits();
 
         ///-----------------------------------------------
-        /// Ooptional quantities: count, units, captions
+        /// Optional quantities: count, units, captions
         ///-----------------------------------------------
 
         /// <summary>
@@ -83,13 +107,13 @@ namespace DataStreamInterface
         /// Returns units of the specified quantity
         /// </summary>
         /// <param name="quanityNr">Zero based quantity number 0 .. quantites count-1</param>
-        Unit GetQuantityUnits(int quanityNr);
+        Unit GetQuantityUnits(int quantityNr);
 
         /// <summary>
         /// Returns caption of the specified quantity
         /// </summary>
         /// <param name="quanityNr">Zero based quantity number 0 .. quantites count-1</param>
-        string GetQuantityCaption(int quanityNr);
+        string GetQuantityCaption(int quantityNr);
 
         ///---------------------------
         /// Datastream data exchange
@@ -98,17 +122,19 @@ namespace DataStreamInterface
         /// <summary>
         /// Retuns 'count' data frames starting with data frame with ID = 'id' 
         /// </summary>
+        /// <param name="meterIx">Index of the meter in range 0 .. (GetMetersCount() - 1)</param>
         /// <param name="id">First frame ID</param>
         /// <param name="count">Frames count</param>
         /// <returns>Selected data frames</returns>
-        DataFrame[] GetFrames(UInt64 id, int count);
+        DataFrame[] GetFrames(int meterIx, Int64 id, int count);
 
         /// <summary>
         /// Returns ID of the data frame where time equals or exceeds the specified time.
         /// When time of the first frame (ID=0) is larger then specified time, function returns 0.
         /// </summary>
+        /// <param name="meterIx">Index of the meter in range 0 .. (GetMetersCount() - 1)</param>
         /// <param name="time">Time</param>
         /// <returns>ID of the data frame at or after the pecified time</returns>
-        UInt64 GetID(double time);
+        Int64 GetID(int meterIx, double time);
     }
 }