diff -ruN zaptel-1.0.7.old/fxstest.c zaptel-1.0.7/fxstest.c
--- zaptel-1.0.7.old/fxstest.c	2004-12-30 21:12:17.000000000 +0100
+++ zaptel-1.0.7/fxstest.c	2005-05-17 12:33:55.594339824 +0200
@@ -28,6 +28,7 @@
 		       "       stats - reports voltages\n"
 		       "       regdump - dumps ProSLIC registers\n"
 		       "       tones - plays a series of tones\n"
+		       "       polarity - changes polarity\n"
 		       "       ring - rings phone\n");
 		exit(1);
 	}
@@ -46,6 +47,24 @@
 			fprintf(stderr, "Phone is ringing...\n");
 			sleep(2);
 		}
+	} else if (!strcasecmp(argv[2], "polarity")) {
+		fprintf(stderr, "Twiddling polarity...\n");
+		x = 0;
+		res = ioctl(fd, ZT_SETPOLARITY, &x);
+		if (res) {
+			fprintf(stderr, "Unable to polarity...\n");
+		} else {
+			fprintf(stderr, "Polarity is forward...\n");
+			sleep(2);
+			x = 1;
+			ioctl(fd, ZT_SETPOLARITY, &x);
+			fprintf(stderr, "Polarity is reversed...\n");
+			sleep(5);
+			x = 0;
+			ioctl(fd, ZT_SETPOLARITY, &x);
+			fprintf(stderr, "Polarity is forward...\n");
+			sleep(2);
+		}
 	} else if (!strcasecmp(argv[2], "tones")) {
 		int x = 0;
 		for (;;) {
diff -ruN zaptel-1.0.7.old/wcfxs.c zaptel-1.0.7/wcfxs.c
--- zaptel-1.0.7.old/wcfxs.c	2005-02-28 01:41:29.000000000 +0100
+++ zaptel-1.0.7/wcfxs.c	2005-05-17 12:33:18.753940416 +0200
@@ -1601,6 +1601,22 @@
 				wcfxs_setreg(wc, chan->chanpos - 1, 64, wc->mod.fxs.lasttxhook[chan->chanpos - 1]);
 		}
 		break;
+	case ZT_SETPOLARITY:
+		if (wc->modtype[chan->chanpos - 1] != MOD_TYPE_FXS)
+			return -EINVAL;
+		if (get_user(x, (int *)data))
+			return -EFAULT;
+		/* Can't change polarity while ringing or when open */
+		if ((wc->mod.fxs.lasttxhook[chan->chanpos -1 ] == 0x04) ||
+		    (wc->mod.fxs.lasttxhook[chan->chanpos -1 ] == 0x00))
+			return -EINVAL;
+
+		if (x)
+			wc->mod.fxs.lasttxhook[chan->chanpos - 1] |= 0x04;
+		else
+			wc->mod.fxs.lasttxhook[chan->chanpos - 1] &= ~0x04;
+		wctdm_setreg(wc, chan->chanpos - 1, 64, wc->mod.fxs.lasttxhook[chan->chanpos - 1]);
+		break;
 	case WCFXS_GET_STATS:
 		if (wc->modtype[chan->chanpos - 1] == MOD_TYPE_FXS) {
 			stats.tipvolt = wcfxs_getreg(wc, chan->chanpos - 1, 80) * -376;
diff -ruN zaptel-1.0.7.old/zaptel.h zaptel-1.0.7/zaptel.h
--- zaptel-1.0.7.old/zaptel.h	2004-09-27 21:50:03.000000000 +0200
+++ zaptel-1.0.7/zaptel.h	2005-05-17 12:33:18.754940264 +0200
@@ -604,6 +604,11 @@
  */
 #define ZT_DYNAMIC_DESTROY	_IOW (ZT_CODE, 81, struct zt_dynamic_span)
 
+/*
+ * Set polarity -- implemented by individual driver.  0 = forward, 1 = reverse
+ */
+#define	ZT_SETPOLARITY		_IOW (ZT_CODE, 92, int)
+  
 /* 
  * Startup or Shutdown a span
  */