diff --git a/src/layer1.c b/src/layer1.c
index 21bc862..1132374 100644
--- a/src/layer1.c
+++ b/src/layer1.c
@@ -11,6 +11,8 @@
 #include "v5x_l1_fsm.h"
 #include "v5x_le_management.h"
 
+extern int test_sa7;
+
 extern struct v5x_instance *v5i;
 
 static struct gsmtap_inst *g_gti = NULL;
@@ -74,10 +76,19 @@ static int inp_sig_cb(unsigned int subsys, unsigned int signal, void __attribute
 		v5x_l1_signal_rcv(v5l, L1_SIGNAL_NO_AIS);
 		break;
 	case S_L_INP_LINE_SA_BITS:
-		if ((isd->sa_bits & 0x40))
+		if ((isd->sa_bits & 0x40)) {
 			v5x_l1_signal_rcv(v5l, L1_SIGNAL_SA7_1);
-		else
+			if (test_sa7) {
+				printf("Currently Sa 7 is set to 1, changing it to 0. (Link ID %d)\n", v5l->id);
+				v5x_l1_signal_snd(v5l, L1_SIGNAL_SA7_0);
+			}
+		} else {
 			v5x_l1_signal_rcv(v5l, L1_SIGNAL_SA7_0);
+			if (test_sa7) {
+				printf("Currently Sa 7 is set to 0, changing it to 1. (Link ID %d)\n", v5l->id);
+				v5x_l1_signal_snd(v5l, L1_SIGNAL_SA7_1);
+			}
+		}
 		break;
 	case S_L_INP_LINE_SLIP_RX:
 		printf("RX slip detected on link %d.\n", v5l->id);
diff --git a/src/main.c b/src/main.c
index b2770ee..b28f57b 100644
--- a/src/main.c
+++ b/src/main.c
@@ -72,6 +72,7 @@ void *tall_v5le_ctx = NULL;
 struct v5x_instance *v5i = NULL;
 
 static int daemonize = 0;
+int test_sa7 = 0;
 
 const char *v5le_copyright =
 	"Copyright (C) 2022 by Harald Welte & Andreas Eversberg\r\n"
@@ -89,6 +90,7 @@ static void print_help()
 	printf(" -s --disable-color\n");
 	printf(" -D --daemonize Fork the process into a background daemon\n");
 	printf(" -V --version Print the version number\n");
+	printf(" -7 --rest-sa7 Continously toggle Sa7 when received. (Do loop interface.)\n");
 
 	printf("\nVTY reference generation:\n");
 	printf("    --vty-ref-mode MODE		VTY reference generation mode (e.g. 'expert').\n");
@@ -133,10 +135,11 @@ static void handle_options(int argc, char **argv)
 			{"disable-color", 0, 0, 's'},
 			{"vty-ref-mode", 1, &long_option, 1},
 			{"vty-ref-xml", 0, &long_option, 2},
+			{"test-sa7", 0, 0, '7'},
 			{0, 0, 0, 0},
 		};
 
-		c = getopt_long(argc, argv, "hc:sVD", long_options, &option_index);
+		c = getopt_long(argc, argv, "hc:sVD7", long_options, &option_index);
 
 		if (c == -1)
 			break;
@@ -162,6 +165,9 @@ static void handle_options(int argc, char **argv)
 		case 'D':
 			daemonize = 1;
 			break;
+		case '7':
+			test_sa7 = 1;
+			break;
 		default:
 			/* ignore */
 			break;