diff --git a/include/asterisk/dsp.h b/include/asterisk/dsp.h
new file mode 100755
index 0000000000..6bf3a16831
--- /dev/null
+++ b/include/asterisk/dsp.h
@@ -0,0 +1,73 @@
+/*
+ * Asterisk -- A telephony toolkit for Linux.
+ *
+ * Convenient Signal Processing routines
+ * 
+ * Copyright (C) 1999, Mark Spencer
+ *
+ * Mark Spencer <markster@linux-support.net>
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License
+ */
+
+#ifndef _ASTERISK_DSP_H
+#define _ASTERISK_DSP_H
+
+#define DSP_FEATURE_SILENCE_SUPPRESS (1 << 0)
+#define DSP_FEATURE_BUSY_DETECT      (1 << 1)
+#define DSP_FEATURE_CALL_PROGRESS    (1 << 2)
+#define DSP_FEATURE_DTMF_DETECT		 (1 << 3)
+
+#define	DSP_DIGITMODE_DTMF			0				/* Detect DTMF digits */
+#define DSP_DIGITMODE_MF			1				/* Detect MF digits */
+
+#define DSP_DIGITMODE_NOQUELCH		(1 << 8)		/* Do not quelch DTMF from in-band */
+#define DSP_DIGITMODE_MUTECONF		(1 << 9)		/* Mute conference */
+#define DSP_DIGITMODE_MUTEMAX		(1 << 10)		/* Delay audio by a frame to try to extra quelch */
+#define DSP_DIGITMODE_RELAXDTMF		(1 << 11)		/* "Radio" mode (relaxed DTMF) */
+
+struct ast_dsp;
+
+struct ast_dsp *ast_dsp_new(void);
+void ast_dsp_free(struct ast_dsp *dsp);
+/* Set threshold value for silence */
+void ast_dsp_set_threshold(struct ast_dsp *dsp, int threshold);
+
+/* Set number of required cadences for busy */
+void ast_dsp_set_busy_count(struct ast_dsp *dsp, int cadences);
+
+/* Scans for progress indication in audio */
+int ast_dsp_call_progress(struct ast_dsp *dsp, struct ast_frame *inf);
+
+/* Return AST_FRAME_NULL frames when there is silence, AST_FRAME_BUSY on 
+   busies, and call progress, all dependent upon which features are enabled */
+struct ast_frame *ast_dsp_process(struct ast_channel *chan, struct ast_dsp *dsp, struct ast_frame *inf, int needlock);
+
+/* Return non-zero if this is silence.  Updates "totalsilence" with the total
+   number of seconds of silence  */
+int ast_dsp_silence(struct ast_dsp *dsp, struct ast_frame *f, int *totalsilence);
+
+/* Return non-zero if historically this should be a busy, request that
+  ast_dsp_silence has already been called */
+int ast_dsp_busydetect(struct ast_dsp *dsp);
+
+/* Return non-zero if DTMF hit was found */
+int ast_dsp_digitdetect(struct ast_dsp *dsp, struct ast_frame *f);
+
+/* Reset total silence count */
+void ast_dsp_reset(struct ast_dsp *dsp);
+
+/* Reset DTMF detector */
+void ast_dsp_digitreset(struct ast_dsp *dsp);
+
+/* Select feature set */
+void ast_dsp_set_features(struct ast_dsp *dsp, int features);
+
+/* Get pending DTMF/MF digits */
+int ast_dsp_getdigits(struct ast_dsp *dsp, char *buf, int max);
+
+/* Set digit mode */
+int ast_dsp_digitmode(struct ast_dsp *dsp, int digitmode);
+
+#endif