--- modem.c.ORG	2012-05-22 16:42:30.000000000 +0200
+++ modem.c	2012-05-22 16:42:25.000000000 +0200
@@ -371,7 +371,7 @@ char *modem_get_s_register(int r)

 		if (modem_command(command, "?") == 1)
 		{
-			log(L_DEBUG, "Got s-register value \"%s\".\n", modem_get_last_result());
+			log(L_DEBUG, "Got s-register %d value \"%s\".\n", r, modem_get_last_result());

 			modem_raw_read(temp, 4);

@@ -897,7 +897,9 @@ int modem_wait(void)
 int modem_count_rings(int needrings)
 {
 	char	line[MODEM_BUFFER_LEN + 1];
-	char *sreg;
+        char   *prefix;
+	char   *sreg;
+        char   *tmpline;
 	int	haverings;
 	int	havesregs;
 	int	havesetup;
@@ -981,7 +983,49 @@ int modem_count_rings(int needrings)

 			voice_init_section();

-			xstrncpy(setup.voice.callerid, &line[15], VOICE_MAX_CALLERID);
+                        // read caller-id and remove leading zeros
+                        tmpline = &line[15];
+			while(*tmpline == '0')
+				tmpline++;
+
+			log(L_DEBUG, "TEST-tmpline %s\n", tmpline);
+			log(L_DEBUG, "TEST-tmpline-length %d\n", strlen(tmpline));
+
+			if (strlen(tmpline) == 0)
+			{
+				// no caller-id has been transmitted
+				xstrncpy(setup.voice.callerid, &line[15], VOICE_MAX_CALLERID);
+			}
+			else
+			{
+				// caller-id has been transmitted
+				prefix = "";
+
+				if ((sreg = modem_get_s_register(21)))
+				{
+					// bit-mapped register. Set on incoming call (during RING) to the value
+					// of octet 3 of calling party number information element (numbering plan).
+					int sreg_val = atoi(sreg);
+
+					if (sreg_val & 32)        // check if bit 6 has been set -> 0x20 - national
+					{
+						// national call
+						prefix = "0";
+						log(L_DEBUG, "check bit 6 -> national call\n", sreg_val);
+					}
+					else if (sreg_val & 16)   // check if bit 5 has been set -> 0x10 - international
+					{
+						// international call
+						prefix = "00";
+						log(L_DEBUG, "check bit 5 -> international call\n", sreg_val);
+					}
+				}
+
+				strncpy(setup.voice.callerid, prefix, 3);
+				xstrncat(setup.voice.callerid, tmpline, VOICE_MAX_CALLERID);
+			}
+
+			log(L_DEBUG, "TEST-setup.voice.callerid %s\n", setup.voice.callerid);

 			voice_user_section(setup.voice.callerid);