--- /root/zaptel-1.4.11/kernel/wctdm.c	2008-04-24 15:17:12.000000000 -0300
+++ wctdm.c	2008-05-12 17:53:11.000000000 -0300
@@ -229,6 +229,8 @@
 		        int lastpol;
 		        int polarity;
 		        int polaritydebounce;
+			int readcid;
+                        unsigned int cidtimer;
 		} fxo;
 		struct fxs {
 			int oldrxhook;
@@ -292,6 +294,7 @@
 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);
 
@@ -373,6 +376,7 @@
 			if (!wc->mod[card].fxo.offhook)
 				zt_hooksig(&wc->chans[card], ZT_RXSIG_RING);
 			wc->mod[card].fxo.ring = 1;
+			wc->mod[card].fxo.readcid = 1;
 		}
 		if (wc->mod[card].fxo.ring && !wc->mod[card].fxo.pegcount) {
 			/* No more ring */
@@ -380,10 +384,33 @@
 				printk("NO RING on %d/%d!\n", wc->span.spanno, card + 1);
 			zt_hooksig(&wc->chans[card], ZT_RXSIG_OFFHOOK);
 			wc->mod[card].fxo.ring = 0;
+			wc->mod[card].fxo.cidtimer = wc->intcount;
+                        wc->mod[card].fxo.readcid = 0;
 		}
 	}
 }
 #endif
+
+static inline void wctdm_dtmfcheck_fakepolarity(struct wctdm *wc, int card, int x)
+{
+       int sample;
+       if (dtmf && (wc->cardflag & (1 << card)) && wc->modtype[card] == MOD_TYPE_FXO && !wc->mod[card].fxo.offhook ) {
+               if(!wc->mod[card].fxo.readcid && !wc->mod[card].fxo.wasringing  &&
+               wc->intcount > wc->mod[card].fxo.cidtimer + 400) {
+                       sample = ZT_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);
+                               zt_qevent_lock(&wc->chans[card], ZT_EVENT_POLARITY);
+                       }
+               } else if(wc->intcount > wc->mod[card].fxo.cidtimer + 2000) {
+                       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;
@@ -414,6 +441,10 @@
 		if (wc->cardflag & (1 << 0))
 			wc->chans[0].readchunk[x] = (readchunk[x]) & 0xff;
 #endif
+		wctdm_dtmfcheck_fakepolarity(wc,0,x);
+		wctdm_dtmfcheck_fakepolarity(wc,1,x);
+		wctdm_dtmfcheck_fakepolarity(wc,2,x);
+		wctdm_dtmfcheck_fakepolarity(wc,3,x);
 	}
 #ifdef AUDIO_RINGCHECK
 	for (x=0;x<wc->cards;x++)
@@ -787,6 +818,8 @@
 				} else if (!res) {
 					if ((fxo->ringdebounce == 0) && fxo->wasringing) {
 						fxo->wasringing = 0;
+						wc->mod[card].fxo.readcid = 0;
+						wc->mod[card].fxo.cidtimer = wc->intcount;
 						if (debug)
 							printk("NO RING on %d/%d!\n", wc->span.spanno, card + 1);
 						zt_hooksig(&wc->chans[card], ZT_RXSIG_OFFHOOK);
@@ -909,18 +942,18 @@
 				fxo->battdebounce = battdebounce / MS_PER_CHECK_HOOK;
 			}
 		}
-	}
 
-	if (fxo->lastpol >= 0) {
-		if (b < 0) {
-			fxo->lastpol = -1;
-			fxo->polaritydebounce = POLARITY_DEBOUNCE / MS_PER_CHECK_HOOK;
-		}
-	} 
-	if (fxo->lastpol <= 0) {
-		if (b > 0) {
-			fxo->lastpol = 1;
-			fxo->polaritydebounce = POLARITY_DEBOUNCE / MS_PER_CHECK_HOOK;
+		if (fxo->lastpol >= 0) {
+			if (b < 0) {
+				fxo->lastpol = -1;
+				fxo->polaritydebounce = POLARITY_DEBOUNCE / MS_PER_CHECK_HOOK;
+			}
+		} 
+		if (fxo->lastpol <= 0) {
+			if (b > 0) {
+				fxo->lastpol = 1;
+				fxo->polaritydebounce = POLARITY_DEBOUNCE / MS_PER_CHECK_HOOK;
+			}
 		}
 	}
 
@@ -2523,6 +2556,7 @@
 module_param(fxorxgain, int, 0600);
 module_param(fxstxgain, int, 0600);
 module_param(fxsrxgain, int, 0600);
+module_param(dtmf, int, 0600);
 #else
 MODULE_PARM(debug, "i");
 MODULE_PARM(loopcurrent, "i");