diff --git a/demux12.txt b/demux12.txt
new file mode 100644
index 0000000..aafc724
--- /dev/null
+++ b/demux12.txt
@@ -0,0 +1,15 @@
+DEF DEMUX12
+    PORT IN A
+    PORT IN S
+    PORT OUT Z0
+    PORT OUT Z1
+
+    NET A1
+    NET B1
+
+    INST NAND11 NAND A  S  A1
+    INST NAND12 NAND A  A1 B1
+    INST NAND13 NAND B1 B1 Z0
+
+    INST NAND21 NAND A1 A1 Z1
+ENDDEF