diff --git a/VERSION b/VERSION
index 826e142463..9b7bc7cfe6 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-v2.1.1
+v2.1.15
\ No newline at end of file
diff --git a/py/htm/encoders/BaseEncoder.py b/py/htm/encoders/BaseEncoder.py
new file mode 100644
index 0000000000..99fbc24dc4
--- /dev/null
+++ b/py/htm/encoders/BaseEncoder.py
@@ -0,0 +1,62 @@
+# ------------------------------------------------------------------------------
+# HTM Community Edition of NuPIC
+# Copyright (C) 2020, David Keeney
+#
+# This program is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Affero Public License version 3 as published by the Free
+# Software Foundation.
+#
+# This program 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 Affero Public License for more details.
+#
+# You should have received a copy of the GNU Affero Public License along with
+# this program.  If not, see http://www.gnu.org/licenses.
+# ------------------------------------------------------------------------------
+
+
+# Base class for all encoders.
+# An encoder converts a value to a sparse distributed representation.
+#
+# Subclasses must implement method encode and Serializable interface.
+# Subclasses can optionally implement method reset.
+#
+# There are several critical properties which all encoders must have:
+#
+# 1) Semantic similarity:  Similar inputs should have high overlap.  Overlap
+# decreases smoothly as inputs become less similar.  Dissimilar inputs have
+# very low overlap so that the output representations are not easily confused.
+#
+# 2) Stability:  The representation for an input does not change during the
+# lifetime of the encoder.
+#
+# 3) Sparsity: The output SDR should have a similar sparsity for all inputs and
+# have enough active bits to handle noise and subsampling.
+#
+# Reference: https://arxiv.org/pdf/1602.05925.pdf
+
+
+# Members dimensions & size describe the shape of the encoded output SDR.
+# For example, a 6 by 4 dimension would be (6,4,)
+# size is the total number of bits in the result.
+# A subclass of the BaseEncoder should be passed the dimension in the constructor.
+# All subclasses must contain an encode( ) method and a reset( ) method.
+
+from abc import ABC, abstractmethod
+import numpy as np
+from htm.bindings.sdr import SDR
+
+class BaseEncoder(ABC):
+
+  @abstractmethod
+  def __init__(dimensions):
+    self.dimensions = dimensions
+    self.size = SDR(dimensions).size
+    
+  @abstractmethod
+  def reset(self):
+    raise NotImplementedError()
+    
+  @abstractmethod
+  def encode(self, input, output):
+    raise NotImplementedError()
\ No newline at end of file
diff --git a/py/htm/encoders/grid_cell_encoder.py b/py/htm/encoders/grid_cell_encoder.py
index f849712d2f..7c72a91108 100644
--- a/py/htm/encoders/grid_cell_encoder.py
+++ b/py/htm/encoders/grid_cell_encoder.py
@@ -20,8 +20,9 @@
 
 from htm.bindings.sdr import SDR
 from htm.bindings.math import Random
+from htm.bindings.encoder import BaseEncoder
 
-class GridCellEncoder:
+class GridCellEncoder(BaseEncoder):
     """
     This Encoder converts a 2-D coordinate into plausible grid cell activity.
     The output SDR is divided into modules.  Each module is a distinct groups of
@@ -50,8 +51,8 @@ def __init__(self,
         encoder uses.  This encoder produces deterministic output.  The seed
         zero is special, seed zero is replaced with a truly random seed.
         """
-        self.size       = size
-        self.dimensions = (size,)
+        super().__init__((size,))
+        
         self.sparsity   = sparsity
         self.periods    = tuple(sorted(float(p) for p in periods))
         assert(len(self.periods) > 0)
@@ -60,14 +61,14 @@ def __init__(self,
         assert(self.sparsity <= 1)
 
         # Assign each module a range of cells in the output SDR.
-        partitions       = np.linspace(0, self.size, num=len(self.periods) + 1)
+        partitions       = np.linspace(0, super().size, num=len(self.periods) + 1)
         partitions       = list(zip(partitions, partitions[1:]))
         self.partitions_ = [(int(round(start)), int(round(stop)))
                                         for start, stop in partitions]
 
         # Assign each module a random offset and orientation.
         rng            = np.random.RandomState(seed = Random(seed).getUInt32())
-        self.offsets_  = rng.uniform(0, max(self.periods)*9, size=(self.size, 2))
+        self.offsets_  = rng.uniform(0, max(self.periods)*9, size=(super().size, 2))
         self.angles_   = []
         self.rot_mats_ = []
         for period in self.periods:
@@ -95,10 +96,10 @@ def encode(self, location, grid_cells=None):
         location = list(location)
         assert(len(location) == 2)
         if grid_cells is None:
-            grid_cells = SDR((self.size,))
+            grid_cells = SDR(super().dimensions)
         else:
             assert(isinstance(grid_cells, SDR))
-            assert(grid_cells.dimensions == [self.size])
+            assert(grid_cells.dimensions == [super().size])
         if any(math.isnan(x) for x in location):
             grid_cells.zero()
             return grid_cells