diff --git a/src/chain/phone-topology.cc b/src/chain/phone-topology.cc
new file mode 100644
index 00000000000..e0a3fb639b7
--- /dev/null
+++ b/src/chain/phone-topology.cc
@@ -0,0 +1,98 @@
+// chain/phone-topology.cc
+
+// Copyright      2015   Johns Hopkins University (author: Daniel Povey)
+//                2015   Xingyu Na
+
+// See ../../COPYING for clarification regarding multiple authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+// THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
+// WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
+// MERCHANTABLITY OR NON-INFRINGEMENT.
+// See the Apache 2 License for the specific language governing permissions and
+// limitations under the License.
+
+#include "chain/phone-topology.h"
+
+namespace kaldi {
+namespace chain {
+
+
+const fst::VectorFst<StdArc>& PhoneTopolgy::TopologyForPhone (int32 phone) {
+  return fsts_[phone];
+}
+
+PhoneTopology::PhoneTopology (int32 num_phones) {
+  fsts_.clear();
+  fsts_.resize(num_phones + 1);
+  for (int32 i = 1; i <= num_phones; i++) {
+    fst::VectorFst<StdArc> fst;
+    fst.AddState();  // state 0
+    fst.SetStart(0); // set start state
+    fst.AddState();  // state 1
+    fst.AddArc(0, StdArc(1, 1, 0.5, 1));
+    fst.AddArc(1, StdArc(2, 2, 0.5, 1));
+    fst.SetFinal(1); // set final state
+    fsts_[i] = fst;
+  }
+}
+
+void PhoneTopology::Write(std::ostream &os, bool binary) const{
+  WriteToken(os, binary, "<PhoneTopology>");
+  if (!binary) os << "\n";
+  int num_phones = fsts_.size() - 1;
+  WriteToken(os, binary, "<NumPhones>");
+  WriteBasicType(os, binary, num_phones);
+  if (!binary) os << "\n";
+  std::vector<fst::VectorFst<StdArc> >::iterator fiter = fsts_.begin(),
+        fend = fsts_.end();
+  for (++fiter; fiter != fend; ++fiter)
+    WriteFstKaldi(os, binary, *fiter);
+  WriteToken(os, binary, "</PhoneTopology>");
+}
+
+void PhoneTopology::Read(std::istream &is, bool binary) const{
+  ExpectToken(is, binary, "<PhoneTopology>");
+  int num_phones;
+  ExpectToken(is, binary, "<NumPhones>");
+  ReadBasicType(is, binary, &num_phones);
+  fsts_.resize(num_phones + 1);
+  std::vector<fst::VectorFst<StdArc> >::iterator fiter = fsts_.begin(),
+        fend = fsts_.end();
+  for (++fiter; fiter != fend; ++fiter)
+    ReadFstKaldi(os, binary, fiter);
+  ExpectToken(is, binary, "</PhoneTopology>");
+}
+
+bool PhonoTopology::IsAlignable() {
+  std::vector<fst::VectorFst<StdArc> >::iterator fiter = fsts_.begin(),
+        fend = fsts_.end();
+  for (++fiter; fiter != fend; ++fiter) {
+    // Get start state symbles
+    unordered_set<int> syms;
+    for (ArcIterator<Fst<Arc> >aiter(*fiter, fiter->Start()); !aiter.Done(); aiter.Next()) {
+      const Arc &arc = aiter.Value();
+      syms.insert(arc.ilabel);
+    }
+    for (StateIterator<StdFst> siter(*fiter); !siter.Done(); siter.Next()) {
+      typename Arc::StateId s = siter.Value();
+      for (ArcIterator<Fst<Arc> >aiter(*fiter, s); !aiter.Done(); aiter.Next()) {
+        const Arc &arc = aiter.Value();
+        if (arc.nextstate == fiter->Start())
+          return false;
+        if (s != fiter->Start() && syms.find(arc.ilabel) != syms.end())
+          return false;
+      }
+    }
+  }
+  return true;
+}
+
+}  // namespace chain
+}  // namespace kaldi
diff --git a/src/chain/phone-topology.h b/src/chain/phone-topology.h
index 2eaec7d124a..cec7e28686d 100644
--- a/src/chain/phone-topology.h
+++ b/src/chain/phone-topology.h
@@ -78,14 +78,14 @@ class PhoneTopology {
 
   void Write(std::ostream &os, bool binary) const;
 
-  void Read(std::istream &is) const;
+  void Read(std::istream &is, bool binary) const;
 
   // returns true if all the phones' FSTs have the following properties:
   //  - the symbols on arcs out of the start-state are disjoint from the
   //    symbols on arcs out of other states.
   //  - there are no arcs ending in the start state.
   bool IsAlignable();
-  private:
+ private:
   void Check();
 
   // index zero is not used.