diff --git a/src/common/call.c b/src/common/call.c
index e3067f3..63832bf 100644
--- a/src/common/call.c
+++ b/src/common/call.c
@@ -203,9 +203,10 @@ typedef struct call {
 	int test_audio_pos;	/* position for test tone toward mobile */
 	int dial_digits;	/* number of digits to be dialed */
 	int loopback;		/* loopback test for echo */
-	int use_mncc_sock;
-	int send_patterns;
-	int release_on_disconnect;
+	int echo_test;		/* send echo back to mobile phone */
+	int use_mncc_sock;	/* use MNCC socket instead of built-in call control */
+	int send_patterns;	/* send patterns towards fixed network */
+	int release_on_disconnect; /* release towards mobile phone, if MNCC call disconnects, don't send disconnect tone */
 
 } call_t;
 
@@ -486,7 +487,7 @@ static void process_timeout(struct timer *timer)
 	}
 }
 
-int call_init(const char *station_id, const char *audiodev, int samplerate, int latency, int dial_digits, int loopback, int use_mncc_sock, int send_patterns, int release_on_disconnect)
+int call_init(const char *station_id, const char *audiodev, int samplerate, int latency, int dial_digits, int loopback, int use_mncc_sock, int send_patterns, int release_on_disconnect, int echo_test)
 {
 	int rc = 0;
 
@@ -497,13 +498,30 @@ int call_init(const char *station_id, const char *audiodev, int samplerate, int
 	call.latspl = latency * samplerate / 1000;
 	call.dial_digits = dial_digits;
 	call.loopback = loopback;
+	call.echo_test = echo_test;
 	call.use_mncc_sock = use_mncc_sock;
 	call.send_patterns = send_patterns;
 	call.release_on_disconnect = release_on_disconnect;
 	call.samplerate = samplerate;
 	strncpy(call.audiodev, audiodev, sizeof(call.audiodev) - 1);
 
-	if (call.use_mncc_sock)
+	if (use_mncc_sock && audiodev[0]) {
+		PDEBUG(DSENDER, DEBUG_ERROR, "You selected MNCC interface, but it cannot be used with call device (headset).\n");
+		rc = -EINVAL;
+		goto error;
+	}
+	if (use_mncc_sock && echo_test) {
+		PDEBUG(DSENDER, DEBUG_ERROR, "You selected MNCC interface, but it cannot be used with echo test.\n");
+		rc = -EINVAL;
+		goto error;
+	}
+	if (audiodev[0] && echo_test) {
+		PDEBUG(DSENDER, DEBUG_ERROR, "You selected call device (headset), but it cannot be used with echo test.\n");
+		rc = -EINVAL;
+		goto error;
+	}
+
+	if (use_mncc_sock)
 		return 0;
 
 	if (!audiodev[0])
@@ -963,6 +981,7 @@ void call_tx_audio(int callref, sample_t *samples, int count)
 	if (!callref)
 		return;
 
+	/* is MNCC us used, forward audio */
 	if (call.use_mncc_sock) {
 		uint8_t buf[sizeof(struct gsm_data_frame) + count * sizeof(int16_t)];
 		struct gsm_data_frame *data = (struct gsm_data_frame *)buf;
@@ -981,15 +1000,17 @@ void call_tx_audio(int callref, sample_t *samples, int count)
 		samples_to_int16((int16_t *)data->data, samples, count);
 
 		mncc_write(buf, sizeof(buf));
-		return;
-	}
-
-	/* save audio from transceiver to jitter buffer */
+	} else
+	/* else, save audio from transceiver to jitter buffer */
 	if (call.sound) {
 		sample_t up[(int)((double)count * call.srstate.factor + 0.5) + 10];
 		count = samplerate_upsample(&call.srstate, samples, count, up);
 		jitter_save(&call.dejitter, up, count);
 	} else
+	/* else, if echo test is used, send echo back to mobile */
+	if (call.echo_test) {
+		call_rx_audio(callref, samples, count);
+	} else
 	/* else, if no sound is used, send test tone to mobile */
 	if (call.state == CALL_CONNECT) {
 		int16_t spl[count];
@@ -1162,7 +1183,7 @@ void call_mncc_recv(uint8_t *buf, int length)
 		PDEBUG(DMNCC, DEBUG_INFO, "Received MNCC disconnect from Network with cause %d\n", mncc->cause.value);
 
 		if (is_process_state(callref) == CALL_CONNECT && call.release_on_disconnect) {
-			PDEBUG(DCALL, DEBUG_INFO, "Releaseing, because we don't send disconnect tones to mobile phone\n");
+			PDEBUG(DCALL, DEBUG_INFO, "Releasing, because we don't send disconnect tones to mobile phone\n");
 
 			PDEBUG(DMNCC, DEBUG_INFO, "Releasing MNCC call towards Network\n");
 			mncc->msg_type = MNCC_REL_IND;
diff --git a/src/common/call.h b/src/common/call.h
index 78c0577..e9462d6 100644
--- a/src/common/call.h
+++ b/src/common/call.h
@@ -9,7 +9,7 @@ enum number_type {
 	TYPE_INTERNATIONAL,
 };
 
-int call_init(const char *station_id, const char *audiodev, int samplerate, int latency, int dial_digits, int loopback, int use_mncc_sock, int send_patterns, int release_on_disconnect);
+int call_init(const char *station_id, const char *audiodev, int samplerate, int latency, int dial_digits, int loopback, int use_mncc_sock, int send_patterns, int release_on_disconnect, int echo_test);
 void call_cleanup(void);
 int call_open_audio(int latspl);
 int call_start_audio(void);
diff --git a/src/common/main_mobile.c b/src/common/main_mobile.c
index eb281c8..60ff519 100644
--- a/src/common/main_mobile.c
+++ b/src/common/main_mobile.c
@@ -49,19 +49,20 @@ int kanal[MAX_SENDER];
 int num_audiodev = 0;
 const char *audiodev[MAX_SENDER] = { "hw:0,0" };
 int use_sdr = 0;
-const char *call_audiodev = "";
+static const char *call_audiodev = "";
 int samplerate = 48000;
-int call_samplerate = 48000;
+static int call_samplerate = 48000;
 int interval = 1;
 int latency = 50;
 int uses_emphasis = 1;
 int do_pre_emphasis = 0;
 int do_de_emphasis = 0;
 double rx_gain = 1.0;
-int use_mncc_sock = 0;
+static int echo_test = 0;
+static int use_mncc_sock = 0;
 const char *mncc_name = "";
-int send_patterns = 1;
-int release_on_disconnect = 1;
+static int send_patterns = 1;
+static int release_on_disconnect = 1;
 int loopback = 0;
 int rt_prio = 0;
 const char *write_tx_wave = NULL;
@@ -115,15 +116,18 @@ void main_mobile_print_help(const char *arg0, const char *ext_usage)
 	printf("        Raise receiver RX level by given gain in dB. This is useful if input\n");
 	printf("        level of the sound device is too low, even after setting maximum level\n");
 	printf("        with the mixer settings. (Works with sound card only.)\n");
+	printf(" -e --echo-test\n");
+	printf("        Use echo test, to send back audio from mobile phone's microphone to\n");
+	printf("        the speaker. (German: 'Blasprobe').\n");
+	printf(" -c --call-device hw:<card>,<device>\n");
+	printf("        Sound card and device number for headset (default = '%s')\n", call_audiodev);
+	printf("    --call-samplerate <rate>\n");
+	printf("        Sample rate of sound device for headset (default = '%d')\n", call_samplerate);
 	printf(" -m --mncc-sock\n");
 	printf("        Disable built-in call contol and offer socket (to LCR)\n");
 	printf(" --mncc-name <name>\n");
 	printf("        '/tmp/bsc_mncc' is used by default, give name to change socket to\n");
 	printf("        '/tmp/bsc_mncc_<name>'. (Useful to run multiple networks.)\n");
-	printf(" -c --call-device hw:<card>,<device>\n");
-	printf("        Sound card and device number for headset (default = '%s')\n", call_audiodev);
-	printf("    --call-samplerate <rate>\n");
-	printf("        Sample rate of sound device for headset (default = '%d')\n", call_samplerate);
 	printf(" -t --tones 0 | 1\n");
 	printf("        Connect call on setup/release to provide classic tones towards fixed\n");
 	printf("        network (default = '%d')\n", send_patterns);
@@ -177,6 +181,7 @@ static struct option main_mobile_long_options[] = {
 	{"pre-emphasis", 0, 0, 'p'},
 	{"de-emphasis", 0, 0, 'd'},
 	{"rx-gain", 1, 0, 'g'},
+	{"echo-test", 0, 0, 'e'},
 	{"mncc-sock", 0, 0, 'm'},
 	{"mncc-name", 1, 0, OPT_MNCC_NAME},
 	{"call-device", 1, 0, 'c'},
@@ -191,7 +196,7 @@ static struct option main_mobile_long_options[] = {
 	{0, 0, 0, 0}
 };
 
-static const char *main_mobile_optstring = "hv:k:a:s:i:b:pdg:mc:t:l:r:";
+static const char *main_mobile_optstring = "hv:k:a:s:i:b:pdg:mec:t:l:r:";
 
 struct option *long_options;
 char *optstring;
@@ -309,6 +314,10 @@ void main_mobile_opt_switch(int c, char *arg0, int *skip_args)
 		rx_gain = pow(10, gain_db / 20.0);
 		*skip_args += 2;
 		break;
+	case 'e':
+		echo_test = 1;
+		*skip_args += 1;
+		break;
 	case 'm':
 		use_mncc_sock = 1;
 		*skip_args += 1;
@@ -431,7 +440,7 @@ void main_mobile(int *quit, int latency, int interval, void (*myhandler)(void),
 	}
 
 	/* init call device */
-	rc = call_init(station_id, call_audiodev, call_samplerate, latency, station_id_digits, loopback, use_mncc_sock, send_patterns, release_on_disconnect);
+	rc = call_init(station_id, call_audiodev, call_samplerate, latency, station_id_digits, loopback, use_mncc_sock, send_patterns, release_on_disconnect, echo_test);
 	if (rc < 0) {
 		fprintf(stderr, "Failed to create call control instance. Quitting!\n");
 		return;
diff --git a/src/common/main_mobile.h b/src/common/main_mobile.h
index 85503bf..e958f2c 100644
--- a/src/common/main_mobile.h
+++ b/src/common/main_mobile.h
@@ -5,7 +5,6 @@ extern int swap_links;
 extern int num_audiodev;
 extern const char *audiodev[];
 extern int use_sdr;
-extern const char *call_audiodev;
 extern int samplerate;
 extern int interval;
 extern int latency;
@@ -13,8 +12,6 @@ extern int uses_emphasis;
 extern int do_pre_emphasis;
 extern int do_de_emphasis;
 extern double rx_gain;
-extern int use_mncc_sock;
-extern int send_patterns;
 extern int loopback;
 extern int rt_prio;
 extern const char *write_rx_wave;