diff --git a/src/phone.c b/src/phone.c
index c52c266..6f09dbf 100644
--- a/src/phone.c
+++ b/src/phone.c
@@ -95,6 +95,12 @@ struct _Phone
 	GtkListStore * co_store;
 	GtkWidget * co_view;
 
+#ifdef DEBUG
+	/* debugging */
+	GtkWidget * de_window;
+	GtkWidget * de_gsm;
+#endif
+
 	/* dialer */
 	GtkWidget * di_window;
 	GtkWidget * di_entry;
@@ -154,6 +160,12 @@ static gboolean _phone_timeout_track(gpointer data);
 
 
 /* public */
+#ifdef DEBUG
+/* prototypes */
+void phone_show_debug(Phone * phone, gboolean show);
+
+
+#endif
 /* functions */
 /* phone_new */
 static gboolean _new_idle(gpointer data);
@@ -190,6 +202,9 @@ Phone * phone_new(char const * device, unsigned int baudrate, int retry,
 	phone->co_window = NULL;
 	phone->co_store = gtk_list_store_new(3, G_TYPE_UINT, G_TYPE_STRING,
 			G_TYPE_STRING);
+#ifdef DEBUG
+	phone->de_window = NULL;
+#endif
 	phone->di_window = NULL;
 	phone->me_window = NULL;
 	phone->me_store = gtk_list_store_new(2, G_TYPE_UINT, G_TYPE_STRING);
@@ -238,6 +253,9 @@ static gboolean _new_idle(gpointer data)
 
 	phone_show_call(phone, FALSE);
 	phone_show_contacts(phone, FALSE);
+#ifdef DEBUG
+	phone_show_debug(phone, TRUE);
+#endif
 	phone_show_dialer(phone, FALSE);
 	phone_show_messages(phone, FALSE);
 	phone_show_write(phone, FALSE);
@@ -771,6 +789,90 @@ void phone_show_contacts(Phone * phone, gboolean show)
 }
 
 
+#ifdef DEBUG
+/* phone_show_debug */
+static struct
+{
+	char const * name;
+	int (*callback)(GSM * gsm);
+} _debug_gsm_commands[] =
+{
+	{ "Answer call",		gsm_call_answer			},
+	{ "Contact list",		gsm_fetch_contact_list		},
+	{ "Hangup call",		gsm_call_hangup			},
+	{ "Message list",		gsm_fetch_message_list		},
+	{ "Operator",			gsm_fetch_operator		},
+	{ "Phone active",		gsm_is_phone_active		},
+	{ "Phone functional",		gsm_is_functional		},
+	{ "Registered",			gsm_is_registered		},
+	{ "Registration",		gsm_fetch_registration		},
+	{ "Signal level",		gsm_fetch_signal_level		},
+	{ "SIM PIN status",		gsm_is_pin_needed		},
+	{ "SIM PIN valid",		gsm_is_pin_valid		},
+	{ NULL,				NULL				}
+};
+
+static void _on_debug_gsm_execute(gpointer data);
+
+void phone_show_debug(Phone * phone, gboolean show)
+{
+	GtkWidget * vbox;
+	GtkWidget * hbox;
+	GtkWidget * widget;
+	size_t i;
+
+	if(phone->de_window == NULL)
+	{
+		phone->de_window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
+		gtk_window_set_default_size(GTK_WINDOW(phone->de_window), 200,
+				300);
+#if GTK_CHECK_VERSION(2, 6, 0)
+		gtk_window_set_icon_name(GTK_WINDOW(phone->de_window),
+				"stock_compile");
+#endif
+		gtk_window_set_title(GTK_WINDOW(phone->de_window), "Debugging");
+		vbox = gtk_vbox_new(FALSE, 0);
+		/* gsm commands */
+		hbox = gtk_hbox_new(FALSE, 0);
+		phone->de_gsm = gtk_combo_box_new_text();
+		for(i = 0; _debug_gsm_commands[i].name != NULL; i++)
+			gtk_combo_box_append_text(GTK_COMBO_BOX(phone->de_gsm),
+					_debug_gsm_commands[i].name);
+		gtk_box_pack_start(GTK_BOX(hbox), phone->de_gsm, TRUE, TRUE, 4);
+		widget = gtk_button_new_from_stock(GTK_STOCK_EXECUTE);
+		gtk_button_set_relief(GTK_BUTTON(widget), GTK_RELIEF_NONE);
+		g_signal_connect_swapped(G_OBJECT(widget), "clicked",
+				G_CALLBACK(_on_debug_gsm_execute), phone);
+		gtk_box_pack_start(GTK_BOX(hbox), widget, FALSE, TRUE, 0);
+		gtk_box_pack_start(GTK_BOX(vbox), hbox, FALSE, TRUE, 4);
+		gtk_container_add(GTK_CONTAINER(phone->de_window), vbox);
+		gtk_widget_show_all(vbox);
+	}
+	if(show)
+		gtk_window_present(GTK_WINDOW(phone->de_window));
+	else
+		gtk_widget_hide(phone->de_window);
+}
+
+static void _on_debug_gsm_execute(gpointer data)
+{
+	Phone * phone = data;
+	gchar * text;
+	size_t i;
+
+	if((text = gtk_combo_box_get_active_text(GTK_COMBO_BOX(phone->de_gsm)))
+			== NULL)
+		return;
+	for(i = 0; _debug_gsm_commands[i].name != NULL; i++)
+		if(strcmp(_debug_gsm_commands[i].name, text) == 0)
+			break;
+	g_free(text);
+	if(_debug_gsm_commands[i].callback != NULL)
+		_debug_gsm_commands[i].callback(phone->gsm);
+}
+#endif
+
+
 /* phone_show_dialer */
 void phone_show_dialer(Phone * phone, gboolean show)
 {