diff --git a/src/OpenFOAM/Make/files b/src/OpenFOAM/Make/files
index ab53484868..116e78eef6 100644
--- a/src/OpenFOAM/Make/files
+++ b/src/OpenFOAM/Make/files
@@ -96,6 +96,7 @@ primitives/functions/Function1/quadraticRamp/quadraticRamp.C
 primitives/functions/Function1/quarterSineRamp/quarterSineRamp.C
 primitives/functions/Function1/quarterCosineRamp/quarterCosineRamp.C
 primitives/functions/Function1/halfCosineRamp/halfCosineRamp.C
+primitives/functions/Function1/squarePulse/squarePulse.C
 primitives/functions/Function1/Table/tableBase.C
 primitives/functions/Function1/Table/TableReader/makeTableReaders.C
 
diff --git a/src/OpenFOAM/primitives/functions/Function1/Ramp/Ramp.C b/src/OpenFOAM/primitives/functions/Function1/Ramp/Ramp.C
index 33925c8bf7..9738b0fd7e 100644
--- a/src/OpenFOAM/primitives/functions/Function1/Ramp/Ramp.C
+++ b/src/OpenFOAM/primitives/functions/Function1/Ramp/Ramp.C
@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     | Website:  https://openfoam.org
-    \\  /    A nd           | Copyright (C) 2017-2020 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2017-2021 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -27,7 +27,7 @@ License
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
-template <class Function1Type>
+template<class Function1Type>
 void Foam::Function1s::Ramp<Function1Type>::read(const dictionary& dict)
 {
     start_ = dict.lookupOrDefault<scalar>("start", 0);
@@ -35,7 +35,7 @@ void Foam::Function1s::Ramp<Function1Type>::read(const dictionary& dict)
 }
 
 
-template <class Function1Type>
+template<class Function1Type>
 Foam::Function1s::Ramp<Function1Type>::Ramp
 (
     const word& name,
@@ -50,14 +50,14 @@ Foam::Function1s::Ramp<Function1Type>::Ramp
 
 // * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
 
-template <class Function1Type>
+template<class Function1Type>
 Foam::Function1s::Ramp<Function1Type>::~Ramp()
 {}
 
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
-template <class Function1Type>
+template<class Function1Type>
 void Foam::Function1s::Ramp<Function1Type>::write(Ostream& os) const
 {
     writeEntry(os, "start", start_);
diff --git a/src/OpenFOAM/primitives/functions/Function1/Ramp/Ramp.H b/src/OpenFOAM/primitives/functions/Function1/Ramp/Ramp.H
index 096635454b..db645bbe6a 100644
--- a/src/OpenFOAM/primitives/functions/Function1/Ramp/Ramp.H
+++ b/src/OpenFOAM/primitives/functions/Function1/Ramp/Ramp.H
@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     | Website:  https://openfoam.org
-    \\  /    A nd           | Copyright (C) 2017-2020 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2017-2021 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -79,7 +79,7 @@ namespace Function1s
                             Class Ramp Declaration
 \*---------------------------------------------------------------------------*/
 
-template <class Function1Type>
+template<class Function1Type>
 class Ramp
 :
     public FieldFunction1<scalar, Function1Type>
diff --git a/src/OpenFOAM/primitives/functions/Function1/objectFunction1/objectFunction1.H b/src/OpenFOAM/primitives/functions/Function1/objectFunction1/objectFunction1.H
index 7dfc14ce74..f635e21639 100644
--- a/src/OpenFOAM/primitives/functions/Function1/objectFunction1/objectFunction1.H
+++ b/src/OpenFOAM/primitives/functions/Function1/objectFunction1/objectFunction1.H
@@ -59,7 +59,7 @@ class objectFunction1
     // Private Classes
 
         //- Tag structure used to deduce type in the templated constructor
-        template <class PrimitiveType>
+        template<class PrimitiveType>
         struct type
         {};
 
@@ -67,7 +67,7 @@ class objectFunction1
     // Private Constructors
 
         //- Construct from an name and a dictionary
-        template <class PrimitiveType>
+        template<class PrimitiveType>
         objectFunction1
         (
             const word& name,
@@ -80,7 +80,7 @@ public:
 
     // Selector
 
-        template <template <class> class ObjectType>
+        template<template<class> class ObjectType>
         static autoPtr<objectFunction1> New
         (
             const word& name,
@@ -99,19 +99,19 @@ public:
     // Member Functions
 
         //- Return value as a function of scalar x
-        template <class PrimitiveType>
+        template<class PrimitiveType>
         PrimitiveType value(const scalar x) const;
 
         //- Return value as a function of scalarField x
-        template <class PrimitiveType>
+        template<class PrimitiveType>
         tmp<Field<PrimitiveType>> value(const scalarField& x) const;
 
         //- Integrate between two scalars
-        template <class PrimitiveType>
+        template<class PrimitiveType>
         PrimitiveType integral(const scalar x1, const scalar x2) const;
 
         //- Integrate between two scalar fields
-        template <class PrimitiveType>
+        template<class PrimitiveType>
         tmp<Field<PrimitiveType>> integral
         (
             const scalarField& x1,
diff --git a/src/OpenFOAM/primitives/functions/Function1/objectFunction1/objectFunction1Templates.C b/src/OpenFOAM/primitives/functions/Function1/objectFunction1/objectFunction1Templates.C
index ff31099c50..27582d90d3 100644
--- a/src/OpenFOAM/primitives/functions/Function1/objectFunction1/objectFunction1Templates.C
+++ b/src/OpenFOAM/primitives/functions/Function1/objectFunction1/objectFunction1Templates.C
@@ -27,7 +27,7 @@ License
 
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
-template <class PrimitiveType>
+template<class PrimitiveType>
 Foam::objectFunction1::objectFunction1
 (
     const word& name,
@@ -44,7 +44,7 @@ Foam::objectFunction1::objectFunction1
 
 // * * * * * * * * * * * * * * * * Selectors * * * * * * * * * * * * * * * * //
 
-template <template <class> class ObjectType>
+template<template<class> class ObjectType>
 Foam::autoPtr<Foam::objectFunction1> Foam::objectFunction1::New
 (
     const word& name,
@@ -81,7 +81,7 @@ Foam::autoPtr<Foam::objectFunction1> Foam::objectFunction1::New
 
 // * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * * //
 
-template <class PrimitiveType>
+template<class PrimitiveType>
 PrimitiveType Foam::objectFunction1::value
 (
     const scalar x
@@ -91,7 +91,7 @@ PrimitiveType Foam::objectFunction1::value
 }
 
 
-template <class PrimitiveType>
+template<class PrimitiveType>
 Foam::tmp<Foam::Field<PrimitiveType>> Foam::objectFunction1::value
 (
     const scalarField& x
@@ -101,7 +101,7 @@ Foam::tmp<Foam::Field<PrimitiveType>> Foam::objectFunction1::value
 }
 
 
-template <class PrimitiveType>
+template<class PrimitiveType>
 PrimitiveType Foam::objectFunction1::integral
 (
     const scalar x1,
@@ -112,7 +112,7 @@ PrimitiveType Foam::objectFunction1::integral
 }
 
 
-template <class PrimitiveType>
+template<class PrimitiveType>
 Foam::tmp<Foam::Field<PrimitiveType>> Foam::objectFunction1::integral
 (
     const scalarField& x1,
diff --git a/src/OpenFOAM/primitives/functions/Function1/squarePulse/squarePulse.C b/src/OpenFOAM/primitives/functions/Function1/squarePulse/squarePulse.C
new file mode 100644
index 0000000000..7faeb7c67c
--- /dev/null
+++ b/src/OpenFOAM/primitives/functions/Function1/squarePulse/squarePulse.C
@@ -0,0 +1,75 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     | Website:  https://openfoam.org
+    \\  /    A nd           | Copyright (C) 2021 OpenFOAM Foundation
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+\*---------------------------------------------------------------------------*/
+
+#include "squarePulse.H"
+
+// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
+
+namespace Foam
+{
+namespace Function1s
+{
+    makeScalarFunction1(squarePulse);
+}
+}
+
+
+// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
+
+void Foam::Function1s::squarePulse::read(const dictionary& dict)
+{
+    start_ = dict.lookupOrDefault<scalar>("start", 0);
+    duration_ = dict.lookup<scalar>("duration");
+}
+
+
+Foam::Function1s::squarePulse::squarePulse
+(
+    const word& name,
+    const dictionary& dict
+)
+:
+    FieldFunction1<scalar, squarePulse>(name)
+{
+    read(dict);
+}
+
+
+// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
+
+Foam::Function1s::squarePulse::~squarePulse()
+{}
+
+
+// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
+
+void Foam::Function1s::squarePulse::write(Ostream& os) const
+{
+    writeEntry(os, "start", start_);
+    writeEntry(os, "duration", duration_);
+}
+
+
+// ************************************************************************* //
diff --git a/src/OpenFOAM/primitives/functions/Function1/squarePulse/squarePulse.H b/src/OpenFOAM/primitives/functions/Function1/squarePulse/squarePulse.H
new file mode 100644
index 0000000000..03785fd70a
--- /dev/null
+++ b/src/OpenFOAM/primitives/functions/Function1/squarePulse/squarePulse.H
@@ -0,0 +1,161 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     | Website:  https://openfoam.org
+    \\  /    A nd           | Copyright (C) 2021 OpenFOAM Foundation
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+Class
+    Foam::Function1s::squarePulse
+
+Description
+    Square pulse function. Takes a value of 0 before \c start, then rises
+    instantaneously to 1, remains at 1 for \c duration, then drops
+    instantaneously back to 0.
+
+    Usage:
+    \verbatim
+        <name> squarePulse;
+        <name>Coeffs
+        {
+            start     10;
+            duration  20;
+        }
+    \endverbatim
+    or
+    \verbatim
+        <name>
+        {
+            type      squarePulse;
+            start     10;
+            duration  20;
+        }
+    \endverbatim
+
+    Where:
+    \table
+        Property | Description  | Required | Default value
+        start    | Start time   | no       | 0
+        duration | Duration     | yes      |
+    \endtable
+
+See also
+    Foam::Function1
+
+SourceFiles
+    squarePulse.C
+
+\*---------------------------------------------------------------------------*/
+
+#ifndef squarePulse_H
+#define squarePulse_H
+
+#include "Function1.H"
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+namespace Foam
+{
+namespace Function1s
+{
+
+/*---------------------------------------------------------------------------*\
+                            Class squarePulse Declaration
+\*---------------------------------------------------------------------------*/
+
+class squarePulse
+:
+    public FieldFunction1<scalar, squarePulse>
+{
+    // Private data
+
+        //- Start-time of the ramp function
+        scalar start_;
+
+        //- Duration of the ramp function
+        scalar duration_;
+
+
+private:
+
+    // Private Member Functions
+
+        //- Read the coefficients from the given dictionary
+        void read(const dictionary& dict);
+
+
+public:
+
+    // Runtime type information
+    TypeName("squarePulse");
+
+
+    // Constructors
+
+        //- Construct from name and dictionary
+        squarePulse
+        (
+            const word& name,
+            const dictionary& dict
+        );
+
+
+    //- Destructor
+    virtual ~squarePulse();
+
+
+    // Member Functions
+
+        //- Return value for time t
+        virtual inline scalar value(const scalar t) const;
+
+        //- Return the integral between times t1 and t2
+        virtual inline scalar integral
+        (
+            const scalar t1,
+            const scalar t2
+        ) const;
+
+        //- Write data to dictionary stream
+        virtual void write(Ostream& os) const;
+
+
+    // Member Operators
+
+        //- Disallow default bitwise assignment
+        void operator=(const squarePulse&) = delete;
+};
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+} // End namespace Function1s
+} // End namespace Foam
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#ifdef NoRepository
+    #include "squarePulseI.H"
+#endif
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#endif
+
+// ************************************************************************* //
diff --git a/src/OpenFOAM/primitives/functions/Function1/squarePulse/squarePulseI.H b/src/OpenFOAM/primitives/functions/Function1/squarePulse/squarePulseI.H
new file mode 100644
index 0000000000..4d21a156cc
--- /dev/null
+++ b/src/OpenFOAM/primitives/functions/Function1/squarePulse/squarePulseI.H
@@ -0,0 +1,47 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     | Website:  https://openfoam.org
+    \\  /    A nd           | Copyright (C) 2021 OpenFOAM Foundation
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+\*---------------------------------------------------------------------------*/
+
+#include "squarePulse.H"
+
+// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
+
+inline Foam::scalar Foam::Function1s::squarePulse::value(const scalar t) const
+{
+    return start_ < t && t < start_ + duration_;
+}
+
+
+inline Foam::scalar Foam::Function1s::squarePulse::integral
+(
+    const scalar t1,
+    const scalar t2
+) const
+{
+    NotImplemented;
+    return NaN;
+}
+
+
+// ************************************************************************* //
diff --git a/tutorials/heatTransfer/chtMultiRegionFoam/heatedDuct/constant/heater/fvOptions b/tutorials/heatTransfer/chtMultiRegionFoam/heatedDuct/constant/heater/fvOptions
index 7125a16203..f4f89cce34 100644
--- a/tutorials/heatTransfer/chtMultiRegionFoam/heatedDuct/constant/heater/fvOptions
+++ b/tutorials/heatTransfer/chtMultiRegionFoam/heatedDuct/constant/heater/fvOptions
@@ -21,9 +21,8 @@ options
     {
         type            semiImplicitSource;
 
-        timeStart       0;
-        duration        1e6;
         selectionMode   all;
+
         volumeMode      specific;
 
         sources
diff --git a/tutorials/heatTransfer/chtMultiRegionFoam/reverseBurner/constant/gas/fvOptions b/tutorials/heatTransfer/chtMultiRegionFoam/reverseBurner/constant/gas/fvOptions
index 95216e67c9..c9a0184e69 100644
--- a/tutorials/heatTransfer/chtMultiRegionFoam/reverseBurner/constant/gas/fvOptions
+++ b/tutorials/heatTransfer/chtMultiRegionFoam/reverseBurner/constant/gas/fvOptions
@@ -15,6 +15,32 @@ FoamFile
 }
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
+ignition
+{
+    type            semiImplicitSource;
+
+    selectionMode   cellSet;
+    cellSet         ignition;
+
+    volumeMode      specific;
+
+    sources
+    {
+        h
+        {
+            explicit
+            {
+                type        scale;
+                scale       squarePulse;
+                start       0;
+                duration    1;
+                value       5e7; // kg/m/s^3
+            }
+            implicit    0;
+        }
+    }
+}
+
 radiation
 {
     type    radiation;
diff --git a/tutorials/incompressible/pimpleFoam/laminar/planarPoiseuille/constant/fvOptions b/tutorials/incompressible/pimpleFoam/laminar/planarPoiseuille/constant/fvOptions
index 31c9ff48b3..1655e6439b 100644
--- a/tutorials/incompressible/pimpleFoam/laminar/planarPoiseuille/constant/fvOptions
+++ b/tutorials/incompressible/pimpleFoam/laminar/planarPoiseuille/constant/fvOptions
@@ -19,8 +19,6 @@ momentumSource
 {
     type            semiImplicitSource;
 
-    timeStart       0.0;
-    duration        1000;
     selectionMode   all;
 
     volumeMode      specific;
diff --git a/tutorials/lagrangian/reactingParticleFoam/filter/constant/fvOptions b/tutorials/lagrangian/reactingParticleFoam/filter/constant/fvOptions
index 4c9a8d6cc2..740241eca3 100644
--- a/tutorials/lagrangian/reactingParticleFoam/filter/constant/fvOptions
+++ b/tutorials/lagrangian/reactingParticleFoam/filter/constant/fvOptions
@@ -48,8 +48,6 @@ massSource
 {
     type            semiImplicitSource;
 
-    timeStart       0.2;
-    duration        2.0;
     selectionMode   points;
     points
     (
@@ -58,29 +56,53 @@ massSource
 
     volumeMode      absolute;
 
+    squarePulse
+    {
+        type            scale;
+        scale           squarePulse;
+        start           0.2;
+        duration        2;
+    }
+
     sources
     {
         rho
         {
-            explicit    1e-4; // kg/s
+            explicit
+            {
+                $squarePulse;
+                value       1e-4; // kg/s
+            }
             implicit    0;
         }
 
         U
         {
-            explicit    (0 0.005 0);
+            explicit
+            {
+                $squarePulse;
+                value       (0 0.005 0);
+            }
             implicit    0;
         }
 
         h
         {
-            explicit    10;
+            explicit
+            {
+                $squarePulse;
+                value       10;
+            }
             implicit    0;
         }
 
         H2O
         {
-            explicit    1e-4; // kg/s
+            explicit
+            {
+                $squarePulse;
+                value       1e-4; // kg/s
+            }
             implicit    0;
         }
     }
diff --git a/tutorials/lagrangian/reactingParticleFoam/simplifiedSiwek/constant/fvOptions b/tutorials/lagrangian/reactingParticleFoam/simplifiedSiwek/constant/fvOptions
index 09ede33087..5c1805bd0c 100644
--- a/tutorials/lagrangian/reactingParticleFoam/simplifiedSiwek/constant/fvOptions
+++ b/tutorials/lagrangian/reactingParticleFoam/simplifiedSiwek/constant/fvOptions
@@ -21,10 +21,12 @@ source1
 
     timeStart       0.1;
     duration        0.4;
+
     selectionMode   cellSet;
     cellSet         ignitionCells;
 
     mode            uniform;
+
     temperature     2000;
 }
 
diff --git a/tutorials/multiphase/interFoam/laminar/wave/constant/fvOptions b/tutorials/multiphase/interFoam/laminar/wave/constant/fvOptions
index 9e46ecc21e..fe7dbff0ab 100644
--- a/tutorials/multiphase/interFoam/laminar/wave/constant/fvOptions
+++ b/tutorials/multiphase/interFoam/laminar/wave/constant/fvOptions
@@ -32,9 +32,6 @@ option1
 
     value           (2 0 0);
     lambda          0.5;
-
-    timeStart       0;
-    duration        1e6;
 }
 
 
diff --git a/tutorials/multiphase/interFoam/laminar/wave/constant/fvOptions.verticalDamping b/tutorials/multiphase/interFoam/laminar/wave/constant/fvOptions.verticalDamping
index 0193a94cf9..c588065ab0 100644
--- a/tutorials/multiphase/interFoam/laminar/wave/constant/fvOptions.verticalDamping
+++ b/tutorials/multiphase/interFoam/laminar/wave/constant/fvOptions.verticalDamping
@@ -31,9 +31,6 @@ option1
     }
 
     lambda          0.5;
-
-    timeStart       0;
-    duration        1e6;
 }
 
 
diff --git a/tutorials/multiphase/multiphaseEulerFoam/laminar/injection/constant/fvOptions b/tutorials/multiphase/multiphaseEulerFoam/laminar/injection/constant/fvOptions
index dba627bc0e..f41fbd8b97 100644
--- a/tutorials/multiphase/multiphaseEulerFoam/laminar/injection/constant/fvOptions
+++ b/tutorials/multiphase/multiphaseEulerFoam/laminar/injection/constant/fvOptions
@@ -21,9 +21,6 @@ options
     {
         type            massSource;
 
-        timeStart       0.1;
-        duration        5;
-
         selectionMode   points;
         points
         (
diff --git a/tutorials/multiphase/multiphaseEulerFoam/laminar/steamInjection/constant/fvOptions b/tutorials/multiphase/multiphaseEulerFoam/laminar/steamInjection/constant/fvOptions
index e21e5c99cd..f0660395db 100644
--- a/tutorials/multiphase/multiphaseEulerFoam/laminar/steamInjection/constant/fvOptions
+++ b/tutorials/multiphase/multiphaseEulerFoam/laminar/steamInjection/constant/fvOptions
@@ -21,9 +21,6 @@ options
     {
         type            massSource;
 
-        timeStart       1;
-        duration        500;
-
         selectionMode   points;
         points
         (