diff --git a/pvDataApp/misc/bitSet.cpp b/pvDataApp/misc/bitSet.cpp
index 8169aff..31d6414 100644
--- a/pvDataApp/misc/bitSet.cpp
+++ b/pvDataApp/misc/bitSet.cpp
@@ -374,5 +374,20 @@ namespace epics { namespace pvData {
             words[i] |= (buffer->getByte() & 0xffL) << (8 * j);
     
     }
+    
+    epicsShareExtern std::ostream& operator<<(std::ostream& o, const BitSet& b)
+    {
+        o << '{';
+        int32 i = b.nextSetBit(0);
+        if (i != -1) {
+            o << i;
+            for (i = b.nextSetBit(i+1); i >= 0; i = b.nextSetBit(i+1)) {
+                int32 endOfRun = b.nextClearBit(i);
+                do { o << ", " << i; } while (++i < endOfRun);
+            }
+        }
+        o << '}';
+        return o;
+    }
 
 }};
diff --git a/pvDataApp/misc/bitSet.h b/pvDataApp/misc/bitSet.h
index ae7357c..be6f231 100644
--- a/pvDataApp/misc/bitSet.h
+++ b/pvDataApp/misc/bitSet.h
@@ -317,6 +317,8 @@ namespace epics { namespace pvData {
          static uint32 bitCount(uint64 i);
 
     };
+    
+    epicsShareExtern std::ostream& operator<<(std::ostream& o, const BitSet& b);
 
 }}
 #endif  /* BITSET_H */