diff --git a/include/osmocom/msc/trau_mux.h b/include/osmocom/msc/trau_mux.h
new file mode 100644
index 0000000..08863bf
--- /dev/null
+++ b/include/osmocom/msc/trau_mux.h
@@ -0,0 +1,70 @@
+/* Simple TRAU frame reflector to route voice calls */
+
+/* (C) 2009 by Harald Welte <laforge@gnumonks.org>
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+/* The "TRAU mux map" defines which particular 16kbit sub-slot (in which E1
+ * timeslot on which E1 interface) should be directly muxed to which other 
+ * sub-slot.  Entries in the mux map are always bi-directional. 
+ *
+ * The idea of all this is to directly switch voice channels in the BSC
+ * from one phone to another.  We do this right now since we don't support
+ * any external interface for voice channels, and in the future as an
+ * optimization to routing them externally.
+ */
+
+#include <stdint.h>
+#include <osmocom/msc/gsm_data.h>
+#include <osmocom/msc/mncc.h>
+
+struct decoded_trau_frame;
+
+/* map a TRAU mux map entry */
+int trau_mux_map(const struct gsm_e1_subslot *src,
+		 const struct gsm_e1_subslot *dst);
+int trau_mux_map_lchan(const struct gsm_lchan *src,	
+			const struct gsm_lchan *dst);
+
+/* unmap a TRAU mux map entry */
+int trau_mux_unmap(const struct gsm_e1_subslot *ss, uint32_t callref);
+
+/* we get called by subchan_demux */
+int trau_mux_input(struct gsm_e1_subslot *src_e1_ss,
+		   const uint8_t *trau_bits, int num_bits);
+
+/* add a trau receiver */
+int trau_recv_lchan(struct gsm_lchan *lchan, uint32_t callref);
+
+/* send trau from application */
+int trau_send_frame(struct gsm_lchan *lchan, struct gsm_data_frame *frame);
+
+/* switch trau muxer to new lchan */
+int switch_trau_mux(struct gsm_lchan *old_lchan, struct gsm_lchan *new_lchan);
+
+/* callback invoked if we receive TRAU frames */
+int subch_cb(struct subch_demux *dmx, int ch, uint8_t *data, int len, void *_priv);
+
+/* TRAU frame transcoding */
+struct msgb *trau_decode_fr(uint32_t callref,
+	const struct decoded_trau_frame *tf);
+struct msgb *trau_decode_efr(uint32_t callref,
+	const struct decoded_trau_frame *tf);
+void trau_encode_fr(struct decoded_trau_frame *tf,
+	const unsigned char *data);
+void trau_encode_efr(struct decoded_trau_frame *tf,
+	const unsigned char *data);