diff --git a/attn/pel/extended_user_header.cpp b/attn/pel/extended_user_header.cpp
new file mode 100644
index 0000000..117ca62
--- /dev/null
+++ b/attn/pel/extended_user_header.cpp
@@ -0,0 +1,59 @@
+#include "extended_user_header.hpp"
+
+namespace attn
+{
+namespace pel
+{
+
+ExtendedUserHeader::ExtendedUserHeader(Stream& pel)
+{
+    unflatten(pel);
+}
+
+void ExtendedUserHeader::flatten(Stream& pel) const
+{
+    pel << _header;
+    pel.write(_mtms, mtmsSize);
+    pel.write(_serverFWVersion.data(), _serverFWVersion.size());
+    pel.write(_subsystemFWVersion.data(), _subsystemFWVersion.size());
+    pel << _reserved4B << _refTime << _reserved1B1 << _reserved1B2
+        << _reserved1B3 << _symptomIdSize << _symptomId;
+}
+
+void ExtendedUserHeader::unflatten(Stream& pel)
+{
+    pel >> _header;
+    pel.read(_mtms, mtmsSize);
+    pel.read(_serverFWVersion.data(), _serverFWVersion.size());
+    pel.read(_subsystemFWVersion.data(), _subsystemFWVersion.size());
+    pel >> _reserved4B >> _refTime >> _reserved1B1 >> _reserved1B2 >>
+        _reserved1B3 >> _symptomIdSize >> _symptomId;
+
+    //_symptomId.resize(_symptomIdSize);
+    pel >> _symptomId;
+}
+
+void ExtendedUserHeader::setSymptomId(const std::string& symptomId)
+{
+    // set symptomId to new symptomId
+    std::copy(symptomId.begin(), symptomId.end(),
+              std::back_inserter(_symptomId));
+
+    // new symptom Id cannot be larger than existing symptom Id
+    if (_symptomId.size() > size_t((_symptomIdSize - 1)))
+    {
+        _symptomId.resize(_symptomIdSize - 1);
+    }
+
+    // null terminate new symptom Id (it may have been smaller)
+    _symptomId.push_back(0);
+
+    // pad if new symptom ID (it may have been smaller)
+    while ((_symptomId.size() != _symptomIdSize))
+    {
+        _symptomId.push_back(0);
+    }
+}
+
+} // namespace pel
+} // namespace attn