Index: drivers/dahdi/wctdm.c
===================================================================
--- drivers/dahdi/wctdm.c	(revision 4441)
+++ drivers/dahdi/wctdm.c	(working copy)
@@ -228,6 +228,8 @@
 		        int lastpol;
 		        int polarity;
 		        int polaritydebounce;
+			int readcid;
+			unsigned int cidtimer;
 		} fxo;
 		struct fxs {
 			int oldrxhook;
@@ -291,6 +293,7 @@
 static int fxorxgain = 0;
 static int fxstxgain = 0;
 static int fxsrxgain = 0;
+static int dtmf = 0;
 
 static int wctdm_init_proslic(struct wctdm *wc, int card, int fast , int manual, int sane);
 
@@ -383,6 +386,31 @@
 	}
 }
 #endif
+
+static inline void wctdm_dtmfcheck_fakepolarity(struct wctdm *wc, int card, int x) 
+{
+	int sample;
+    /* only look for sound on the line if dtmf flag is on, it is an fxo card and line is onhook */ 
+	if (!dtmf || !(wc->cardflag & (1 << card)) || !(wc->modtype[card] == MOD_TYPE_FXO) || wc->mod[card].fxo.offhook ) 
+        return;
+
+    /* don't look for noise if we're already processing it, or there is a ringing tone */
+	if(!wc->mod[card].fxo.readcid && !wc->mod[card].fxo.wasringing  &&
+		wc->intcount > wc->mod[card].fxo.cidtimer + 400 ) {
+		sample = DAHDI_XLAW(wc->chans[card].readchunk[x], (&(wc->chans[card])));
+		if (sample > 16000 || sample < -16000) {
+			wc->mod[card].fxo.readcid = 1;
+			wc->mod[card].fxo.cidtimer = wc->intcount;
+			if (debug) printk("DTMF CLIP on %i\n",card+1);
+			dahdi_qevent_lock(&wc->chans[card], DAHDI_EVENT_POLARITY);
+		}
+	} else if(wc->mod[card].fxo.readcid && wc->intcount > wc->mod[card].fxo.cidtimer + 2000) {
+        /* reset flags if it's been a while */
+		wc->mod[card].fxo.cidtimer = wc->intcount;
+		wc->mod[card].fxo.readcid = 0;
+	}
+}
+ 
 static inline void wctdm_receiveprep(struct wctdm *wc, unsigned char ints)
 {
 	volatile unsigned int *readchunk;
@@ -397,21 +425,29 @@
 #ifdef __BIG_ENDIAN
 		if (wc->cardflag & (1 << 3))
 			wc->chans[3].readchunk[x] = (readchunk[x]) & 0xff;
+		wctdm_dtmfcheck_fakepolarity(wc, 3, x);
 		if (wc->cardflag & (1 << 2))
 			wc->chans[2].readchunk[x] = (readchunk[x] >> 8) & 0xff;
+		wctdm_dtmfcheck_fakepolarity(wc, 2, x);
 		if (wc->cardflag & (1 << 1))
 			wc->chans[1].readchunk[x] = (readchunk[x] >> 16) & 0xff;
+		wctdm_dtmfcheck_fakepolarity(wc, 1, x);
 		if (wc->cardflag & (1 << 0))
 			wc->chans[0].readchunk[x] = (readchunk[x] >> 24) & 0xff;
+		wctdm_dtmfcheck_fakepolarity(wc, 0, x);
 #else
 		if (wc->cardflag & (1 << 3))
 			wc->chans[3].readchunk[x] = (readchunk[x] >> 24) & 0xff;
+		wctdm_dtmfcheck_fakepolarity(wc, 3, x);
 		if (wc->cardflag & (1 << 2))
 			wc->chans[2].readchunk[x] = (readchunk[x] >> 16) & 0xff;
+		wctdm_dtmfcheck_fakepolarity(wc, 2, x);
 		if (wc->cardflag & (1 << 1))
 			wc->chans[1].readchunk[x] = (readchunk[x] >> 8) & 0xff;
+		wctdm_dtmfcheck_fakepolarity(wc, 1, x);
 		if (wc->cardflag & (1 << 0))
 			wc->chans[0].readchunk[x] = (readchunk[x]) & 0xff;
+		wctdm_dtmfcheck_fakepolarity(wc, 0, x);
 #endif
 	}
 #ifdef AUDIO_RINGCHECK
@@ -786,6 +822,8 @@
 				} else if (!res) {
 					if ((fxo->ringdebounce == 0) && fxo->wasringing) {
 						fxo->wasringing = 0;
+ 						fxo->readcid = 0;
+ 						fxo->cidtimer = wc->intcount;
 						if (debug)
 							printk("NO RING on %d/%d!\n", wc->span.spanno, card + 1);
 						dahdi_hooksig(&wc->chans[card], DAHDI_RXSIG_OFFHOOK);
@@ -802,6 +840,8 @@
 				if (fxo->ringdebounce >= DAHDI_CHUNKSIZE * ringdebounce) {
 					if (!fxo->wasringing) {
 						fxo->wasringing = 1;
+	 					fxo->readcid = 0;
+	 					fxo->cidtimer = wc->intcount;
 						dahdi_hooksig(&wc->chans[card], DAHDI_RXSIG_RING);
 						if (debug)
 							printk("RING on %d/%d!\n", wc->span.spanno, card + 1);
@@ -2489,6 +2529,7 @@
 module_param(battthresh, uint, 0600);
 module_param(ringdebounce, int, 0600);
 module_param(fwringdetect, int, 0600);
+module_param(dtmf, int, 0600);
 module_param(alawoverride, int, 0600);
 module_param(fastpickup, int, 0600);
 module_param(fxotxgain, int, 0600);
Index: drivers/dahdi/wctdm24xxp/wctdm24xxp.h
===================================================================
--- drivers/dahdi/wctdm24xxp/wctdm24xxp.h	(revision 4441)
+++ drivers/dahdi/wctdm24xxp/wctdm24xxp.h	(working copy)
@@ -230,6 +230,8 @@
 			int lastpol;
 			int polarity;
 			int polaritydebounce;
+			int readcid;
+			unsigned int cidtimer;
 		} fxo;
 		struct fxs {
 			int oldrxhook;
Index: drivers/dahdi/wctdm24xxp/base.c
===================================================================
--- drivers/dahdi/wctdm24xxp/base.c	(revision 4441)
+++ drivers/dahdi/wctdm24xxp/base.c	(working copy)
@@ -212,6 +212,7 @@
 /* See vpmnlptype = 4 for more info */
 static int vpmnlpmaxsupp = 0;
 #endif
+static int dtmf = 0;
 
 static int wctdm_init_proslic(struct wctdm *wc, int card, int fast , int manual, int sane);
 
@@ -840,6 +841,30 @@
 #endif
 }
 
+static inline void wctdm_dtmfcheck_fakepolarity(struct wctdm *wc, int card, int x) 
+{
+	int sample;
+    /* only look for sound on the line if dtmf flag is on, it is an fxo card and line is onhook */ 
+	if (!dtmf || !(wc->cardflag & (1 << card)) || !(wc->modtype[card] == MOD_TYPE_FXO) || wc->mods[card].fxo.offhook ) 
+        return;
+
+    /* don't look for noise if we're already processing it, or there is a ringing tone */
+	if (!wc->mods[card].fxo.readcid && !wc->mods[card].fxo.wasringing  &&
+		 wc->intcount > wc->mods[card].fxo.cidtimer + 400 ) {
+		sample = DAHDI_XLAW(wc->chans[card].readchunk[x], (&(wc->chans[card])));
+		if (sample > 16000 || sample < -16000) {
+			wc->mods[card].fxo.readcid = 1;
+			wc->mods[card].fxo.cidtimer = wc->intcount;
+			if (debug) printk("DTMF CLIP on %i\n",card+1);
+			dahdi_qevent_lock(&wc->chans[card], DAHDI_EVENT_POLARITY);
+		}
+	} else if (wc->mods[card].fxo.readcid && wc->intcount > wc->mods[card].fxo.cidtimer + 2000) {
+        /* reset flags if it's been a while */
+		wc->mods[card].fxo.cidtimer = wc->intcount;
+		wc->mods[card].fxo.readcid = 0;
+	}
+}
+ 
 static inline void wctdm_receiveprep(struct wctdm *wc, unsigned char *readchunk)
 {
 	int x,y;
@@ -863,6 +888,7 @@
 				}
 			}	
 			cmd_decifer(wc, readchunk, y);
+			wctdm_dtmfcheck_fakepolarity(wc,y,x);
 		}
 #ifdef VPM_SUPPORT
 		if (wc->vpm) {
@@ -1156,6 +1182,8 @@
 				} else if (!res) {
 					if ((fxo->ringdebounce == 0) && fxo->wasringing) {
 						fxo->wasringing = 0;
+ 						fxo->readcid = 0;
+ 						fxo->cidtimer = wc->intcount;
 						if (debug)
 							printk("NO RING on %d/%d!\n", wc->span.spanno, card + 1);
 						dahdi_hooksig(&wc->chans[card], DAHDI_RXSIG_OFFHOOK);
@@ -1183,6 +1211,8 @@
 				if (fxo->ringdebounce <= 0) {
 					if (fxo->wasringing) {
 						fxo->wasringing = 0;
+	 					fxo->readcid = 0;
+	 					fxo->cidtimer = wc->intcount;
 						dahdi_hooksig(&wc->chans[card], DAHDI_RXSIG_OFFHOOK);
 						if (debug)
 							printk("NO RING on %d/%d!\n", wc->span.spanno, card + 1);
@@ -3997,6 +4027,7 @@
 module_param(fxsrxgain, int, 0600);
 module_param(ringdebounce, int, 0600);
 module_param(fwringdetect, int, 0600);
+module_param(dtmf, int, 0600);
 module_param(latency, int, 0600);
 #ifdef VPM_SUPPORT
 module_param(vpmsupport, int, 0600);