diff --git a/src/Makefile.am b/src/Makefile.am
index b515058..c07e3b4 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -10,6 +10,7 @@ osmo_v5_le_SOURCES = logging.c \
 		     v5x_data.c \
 		     v5le_vty.c \
 		     lapv5.c \
+		     layer1.c \
 		     v5x_protocol.c \
 		     v5x_l1_fsm.c \
 		     v5x_le_ctrl_fsm.c \
diff --git a/src/layer1.c b/src/layer1.c
new file mode 100644
index 0000000..21bc862
--- /dev/null
+++ b/src/layer1.c
@@ -0,0 +1,386 @@
+
+#include <osmocom/abis/e1_input.h>
+#include <osmocom/core/gsmtap.h>
+#include <osmocom/core/gsmtap_util.h>
+#include <osmocom/core/signal.h>
+
+#include "v5x_internal.h"
+#include "v5x_protocol.h"
+#include "lapv5.h"
+#include "layer1.h"
+#include "v5x_l1_fsm.h"
+#include "v5x_le_management.h"
+
+extern struct v5x_instance *v5i;
+
+static struct gsmtap_inst *g_gti = NULL;
+
+/* only temporarily until this is in libosmocore gsmtap.h */
+#ifndef GSMTAP_E1T1_V5EF
+#define GSMTAP_E1T1_V5EF	0x06
+#endif
+
+static inline struct e1inp_line *e1_line_from_link(struct v5x_link *v5l)
+{
+	struct e1inp_line *e1_line;
+
+	if (v5l->e1_line < 0)
+		return NULL;
+	e1_line = e1inp_line_find(v5l->e1_line);
+	if (!e1_line)
+		return NULL;
+
+	return e1_line;
+}
+
+/* Callback function to receive L1 signal from E1 port */
+static int inp_sig_cb(unsigned int subsys, unsigned int signal, void __attribute__((unused)) *handler_data,
+	void *signal_data)
+{
+	struct input_signal_data *isd = signal_data;
+	struct v5x_interface *v5if;
+	struct v5x_link *v5l;
+
+	if (subsys != SS_L_INPUT)
+		return 0;
+
+	/* no interface */
+	if (llist_empty(&v5i->interfaces))
+		return 0;
+	v5if = llist_first_entry(&v5i->interfaces, struct v5x_interface, list);
+
+	/* not used by any link */
+	v5l = v5x_link_find_e1_line(v5if, isd->line->num);
+	if (!v5l)
+		return 0;
+
+	switch (signal) {
+	case S_L_INP_LINE_LOS:
+		v5x_l1_signal_rcv(v5l, L1_SIGNAL_LOS);
+		break;
+	case S_L_INP_LINE_NOLOS:
+		v5x_l1_signal_rcv(v5l, L1_SIGNAL_NO_LOS);
+		break;
+	case S_L_INP_LINE_RAI:
+		v5x_l1_signal_rcv(v5l, L1_SIGNAL_RAI);
+		break;
+	case S_L_INP_LINE_NORAI:
+		v5x_l1_signal_rcv(v5l, L1_SIGNAL_NO_RAI);
+		break;
+	case S_L_INP_LINE_AIS:
+		v5x_l1_signal_rcv(v5l, L1_SIGNAL_AIS);
+		break;
+	case S_L_INP_LINE_NOAIS:
+		v5x_l1_signal_rcv(v5l, L1_SIGNAL_NO_AIS);
+		break;
+	case S_L_INP_LINE_SA_BITS:
+		if ((isd->sa_bits & 0x40))
+			v5x_l1_signal_rcv(v5l, L1_SIGNAL_SA7_1);
+		else
+			v5x_l1_signal_rcv(v5l, L1_SIGNAL_SA7_0);
+		break;
+	case S_L_INP_LINE_SLIP_RX:
+		printf("RX slip detected on link %d.\n", v5l->id);
+		break;
+	case S_L_INP_LINE_SLIP_TX:
+		printf("TX slip detected on link %d.\n", v5l->id);
+		break;
+	default:
+		;
+	}
+
+	return 0;
+}
+
+/* Send L1 signal to E1 port */
+int v5x_l1_signal_snd(struct v5x_link *v5l, enum l1_signal_prim prim)
+{
+	struct e1inp_line *e1_line;
+
+	/* no line assigned */
+	if (v5l->e1_line < 0)
+		return 0;
+	e1_line = e1inp_line_find(v5l->e1_line);
+	if (!e1_line)
+		return 0;
+
+	switch (prim) {
+	case L1_SIGNAL_SA7_0:
+		e1inp_ts_set_sa_bits(e1_line, 0xbf);
+		break;
+	case L1_SIGNAL_SA7_1:
+		e1inp_ts_set_sa_bits(e1_line, 0xff);
+		break;
+	default:
+		;
+	}
+
+	return 0;
+}
+
+/* data L1 -> L2 from E1 interface */
+static void hdlc_rx_cb(struct e1inp_ts *ts, struct msgb *msg)
+{
+	struct v5x_interface *v5if;
+	struct v5x_link *v5l;
+
+	/* no interface */
+	if (llist_empty(&v5i->interfaces)) {
+		msgb_free(msg);
+		return;
+	}
+	v5if = llist_first_entry(&v5i->interfaces, struct v5x_interface, list);
+
+	/* not used by any link */
+	v5l = v5x_link_find_e1_line(v5if, ts->line->num);
+	if (!v5l) {
+		msgb_free(msg);
+		return;
+	}
+
+	LOGP(DLINP, LOGL_DEBUG, "Link %d L1->L2: %s\n", v5l->id, msgb_hexdump(msg));
+
+	/* send V5 data via gsmtap so wireshark can receive + decode it */
+	gsmtap_send_ex(g_gti, GSMTAP_TYPE_E1T1, v5l->id, ts->num, GSMTAP_E1T1_V5EF,
+			0, 0, 0, 0, msgb_data(msg), msgb_length(msg));
+
+	lapv5ef_rx(v5l, msg);
+}
+
+/* data B-channel data from E1 interface */
+static void raw_rx_cb(struct e1inp_ts *ts, struct msgb *msg)
+{
+	struct v5x_interface *v5if;
+	struct v5x_link *v5l;
+	struct v5x_user_port *v5up;
+
+	/* no interface */
+	if (llist_empty(&v5i->interfaces)) {
+		msgb_free(msg);
+		return;
+	}
+	v5if = llist_first_entry(&v5i->interfaces, struct v5x_interface, list);
+
+	/* not used by any link */
+	v5l = v5x_link_find_e1_line(v5if, ts->line->num);
+	if (!v5l) {
+		msgb_free(msg);
+		return;
+	}
+	v5up = v5l->ts[ts->num].v5up;
+
+	/* not used by any user port */
+	if (!v5up) {
+		msgb_free(msg);
+		return;
+	}
+
+	/* we want B-channel data flipped */
+	osmo_revbytebits_buf(msg->data, msg->len);
+				
+	/* if assigned and active, send B-channel data to socket interface */
+	if (v5up->ts[0] && v5up->ts[0]->nr == ts->num && v5up->ts_activated[0])
+		ph_socket_tx_msg(&v5up->ph_socket, 1, PH_PRIM_DATA_IND, msg->data, msg->len);
+	if (v5up->ts[1] && v5up->ts[1]->nr == ts->num && v5up->ts_activated[1])
+		ph_socket_tx_msg(&v5up->ph_socket, 2, PH_PRIM_DATA_IND, msg->data, msg->len);
+	msgb_free(msg);
+}
+
+/* send HDLC frame to signaling channel (from ISDN) */
+int ph_data_req_hdlc(struct msgb *msg, struct v5x_interface *v5if)
+{
+	struct e1inp_line *e1_line;
+	e1_line = e1_line_from_link(v5if->cc_link);
+	if (!e1_line) {
+		msgb_free(msg);
+		return 0;
+	}
+
+	LOGP(DLINP, LOGL_DEBUG, "Link %d L2->L1: %s\n", v5if->cc_link->id, msgb_hexdump(msg));
+
+	struct e1inp_ts *ts = &e1_line->ts[v5if->cc_link->c_channel[0].ts->nr - 1];
+
+	/* send V5 data via gsmtap so wireshark can receive + decode it */
+	gsmtap_send_ex(g_gti, GSMTAP_TYPE_E1T1, v5if->cc_link->id | GSMTAP_ARFCN_F_UPLINK, ts->num, GSMTAP_E1T1_V5EF,
+			0, 0, 0, 0, msgb_data(msg), msgb_length(msg));
+
+	return e1inp_ts_send_hdlc(ts, msg);
+}
+
+/* send HDLC frame to signaling channel (from DL) */
+int ph_data_req_dl_cc(struct msgb *msg, void *cbdata)
+{
+	struct v5x_interface *v5if = (struct v5x_interface *)cbdata;
+	struct e1inp_line *e1_line;
+
+	e1_line = e1_line_from_link(v5if->cc_link);
+	if (!e1_line) {
+		msgb_free(msg);
+		return 0;
+	}
+
+	struct e1inp_ts *ts = &e1_line->ts[v5if->cc_link->c_channel[0].ts->nr - 1];
+
+	/* add frame relay header */
+	msg->l2h = msgb_push(msg, 2);
+	msg->l2h[0] = msg->l2h[2] & 0xfd;
+	msg->l2h[1] = msg->l2h[3];
+
+	LOGP(DLINP, LOGL_DEBUG, "Link %d L2->L1: %s\n", v5if->cc_link->id, msgb_hexdump(msg));
+
+	/* send V5 data via gsmtap so wireshark can receive + decode it */
+	gsmtap_send_ex(g_gti, GSMTAP_TYPE_E1T1, v5if->cc_link->id | GSMTAP_ARFCN_F_UPLINK, ts->num, GSMTAP_E1T1_V5EF,
+			0, 0, 0, 0, msgb_data(msg), msgb_length(msg));
+
+	return e1inp_ts_send_hdlc(ts, msg);
+}
+
+/* send HDLC frame to protection link (from DL) */
+int ph_data_req_dl_prot(struct msgb *msg, void *cbdata)
+{
+	struct v5x_link *v5l = (struct v5x_link *)cbdata;
+	struct e1inp_line *e1_line;
+
+	e1_line = e1_line_from_link(v5l);
+	if (!e1_line) {
+		msgb_free(msg);
+		return 0;
+	}
+
+	struct e1inp_ts *ts = &e1_line->ts[v5l->c_channel[0].ts->nr - 1];
+
+	/* add frame relay header */
+	msg->l2h = msgb_push(msg, 2);
+	msg->l2h[0] = msg->l2h[2] & 0xfd;
+	msg->l2h[1] = msg->l2h[3];
+
+	LOGP(DLINP, LOGL_DEBUG, "Link %d L2->L1: %s\n", v5l->id, msgb_hexdump(msg));
+
+	/* send V5 data via gsmtap so wireshark can receive + decode it */
+	gsmtap_send_ex(g_gti, GSMTAP_TYPE_E1T1, v5l->id | GSMTAP_ARFCN_F_UPLINK, ts->num, GSMTAP_E1T1_V5EF,
+			0, 0, 0, 0, msgb_data(msg), msgb_length(msg));
+
+	return e1inp_ts_send_hdlc(ts, msg);
+}
+
+/* send raw (B-channel) data to E1 interface */
+static int ph_data_req_raw(struct v5x_link *v5l, struct msgb *msg, int ts_nr)
+{
+	struct e1inp_line *e1_line;
+
+	/* no line assigned */
+	e1_line = e1_line_from_link(v5l);
+	if (!e1_line) {
+		msgb_free(msg);
+		return 0;
+	}
+
+	/* we want B-channel data flipped */
+	osmo_revbytebits_buf(msg->data, msg->len);
+				
+	struct e1inp_ts *ts = &e1_line->ts[ts_nr-1];
+
+	return e1inp_ts_send_raw(ts, msg);
+}
+
+/* receive message from PH-socket */
+void ph_socket_rx_cb(ph_socket_t *s, int channel, uint8_t prim, uint8_t *data, int length)
+{
+	struct v5x_user_port *v5up = s->priv;
+
+	switch (prim) {
+	case PH_PRIM_CTRL_REQ:
+		/* deactivate channels, if active */
+		if ((channel == 0 || channel == 3) && length && *data == PH_CTRL_BLOCK) {
+			v5x_le_channel_unassign(v5up, 1);
+			v5x_le_channel_unassign(v5up, 2);
+		}
+		v5x_le_nat_ph_rcv(v5up, prim, data, length);
+		break;
+	case PH_PRIM_ACT_REQ:
+		if (channel == 1 || channel == 2) {
+			v5x_le_channel_assign(v5up, channel);
+			ph_socket_tx_msg(s, channel, PH_PRIM_ACT_IND, NULL, 0);
+			break;
+		}
+		v5x_le_nat_ph_rcv(v5up, prim, data, length);
+		break;
+	case PH_PRIM_DACT_REQ:
+		if (channel == 1 || channel == 2) {
+			v5x_le_channel_unassign(v5up, channel);
+			ph_socket_tx_msg(s, channel, PH_PRIM_DACT_IND, NULL, 0);
+			break;
+		}
+		v5x_le_nat_ph_rcv(v5up, prim, data, length);
+		break;
+	case PH_PRIM_DATA_REQ:
+		if (v5up->type == V5X_USER_TYPE_PSTN && channel == 0) {
+			struct msgb *msg = msgb_alloc_headroom(length + 32, 32, "V5 PSTN MSG");
+			memcpy(msgb_put(msg, length), data, length);
+			v5x_le_nat_fe_rcv(v5up, msg);
+		} else if (v5up->type == V5X_USER_TYPE_ISDN && channel == 3) {
+			struct msgb *msg = msgb_alloc_headroom(length + 32, 32, "V5 EF MSG");
+			memcpy(msgb_put(msg, length), data, length);
+			lapv5ef_tx(v5up, msg);
+		} else if ((channel == 1 || channel == 2) && v5up->ts[channel - 1]) {
+			struct msgb *msg = msgb_alloc_headroom(length + 32, 32, "B MSG");
+			memcpy(msgb_put(msg, length), data, length);
+			ph_data_req_raw(v5up->ts[channel - 1]->link, msg, v5up->ts[channel - 1]->nr);
+		}
+		/* always confirm */
+		ph_socket_tx_msg(s, channel, PH_PRIM_DATA_CNF, NULL, 0);
+		break;
+	}
+}
+
+//FIXME: we use HDLC
+static int v5le_rx_sign(struct msgb *msg)
+{
+	LOGP(DLMI, LOGL_NOTICE, "Rx: %s\n", msgb_hexdump(msg));
+
+	msgb_free(msg);
+
+	return 0;
+}
+
+static const struct e1inp_line_ops v5le_e1_line_ops = {
+	.sign_link_up = NULL,
+	.sign_link_down = NULL,
+	.sign_link = v5le_rx_sign,
+};
+
+/* init all E1 lines and register input signals */
+int e1_init(void)
+{
+	struct e1inp_line *e1_line;
+	int i, ts;
+
+	g_gti = gsmtap_source_init("224.0.0.1", GSMTAP_UDP_PORT, 0);
+	OSMO_ASSERT(g_gti);
+	gsmtap_source_add_sink(g_gti);
+
+	for (i = 0; i < 256; i++) {
+		e1_line = e1inp_line_find(i);
+		if (!e1_line)
+			continue;
+
+		e1inp_line_bind_ops(e1_line, &v5le_e1_line_ops);
+
+		for (ts = 1; ts <= 31; ts++) {
+			struct e1inp_ts *e1_ts = &e1_line->ts[ts-1];
+			if (ts == 16) { // FIXME: make this depending on c_channel
+				//e1inp_ts_config_sign(e1_ts, e1_line);
+				//e1inp_sign_link_create(e1_ts, E1INP_SIGN_NONE, NULL, 115/*TEI*/, 0/*SAPI*/);
+				e1inp_ts_config_hdlc(e1_ts, e1_line, hdlc_rx_cb);
+			} else
+				e1inp_ts_config_raw(e1_ts, e1_line, raw_rx_cb);
+		}
+
+		e1inp_line_update(e1_line);
+	}
+
+	osmo_signal_register_handler(SS_L_INPUT, inp_sig_cb, NULL);
+
+	return 0;
+}
+
diff --git a/src/layer1.h b/src/layer1.h
new file mode 100644
index 0000000..8829c71
--- /dev/null
+++ b/src/layer1.h
@@ -0,0 +1,18 @@
+
+enum l1_signal_prim {
+	L1_SIGNAL_LOS,
+	L1_SIGNAL_NO_LOS,
+	L1_SIGNAL_RAI,
+	L1_SIGNAL_NO_RAI,
+	L1_SIGNAL_AIS,
+	L1_SIGNAL_NO_AIS,
+	L1_SIGNAL_SA7_1,
+	L1_SIGNAL_SA7_0,
+};
+
+int v5x_l1_signal_snd(struct v5x_link *v5l, enum l1_signal_prim prim);
+int ph_data_req_hdlc(struct msgb *msg, struct v5x_interface *v5if);
+int ph_data_req_dl_cc(struct msgb *msg, void *cbdata);
+int ph_data_req_dl_prot(struct msgb *msg, void *cbdata);
+void ph_socket_rx_cb(ph_socket_t *s, int channel, uint8_t prim, uint8_t *data, int length);
+int e1_init(void);
diff --git a/src/v5x_internal.h b/src/v5x_internal.h
index 706fb2c..a3a5752 100644
--- a/src/v5x_internal.h
+++ b/src/v5x_internal.h
@@ -232,7 +232,7 @@ struct v5x_interface {
 struct v5x_l1_proto {
 	struct v5x_link *v5l;			/* back pointer */
 	struct osmo_fsm_inst *fi;		/* L1 FSM */
-	int los, rai, ais, sa7_zero;		/* RX signal states */
+	int los, rai, ais, sa7;			/* RX signal states */
 };
 
 struct v5x_ctrl_proto {
diff --git a/src/v5x_l1_fsm.c b/src/v5x_l1_fsm.c
index 95aea2b..ceb65b8 100644
--- a/src/v5x_l1_fsm.c
+++ b/src/v5x_l1_fsm.c
@@ -320,7 +320,7 @@ static void l1_fsm_le4_internal_fail(struct osmo_fsm_inst *fi, uint32_t event, v
 		 * We must do this, because there is no frame reception to trigger this.
 		 */
 		if (!l1->los && !l1->rai && !l1->ais) {
-			if (l1->sa7_zero)
+			if (l1->sa7 == 0)
 				osmo_fsm_inst_dispatch(fi, V5X_L1FSM_E_NORMAL_Sa7, NULL);
 			else
 				osmo_fsm_inst_dispatch(fi, V5X_L1FSM_E_NORMAL, NULL);
@@ -583,6 +583,7 @@ struct v5x_l1_proto *v5x_l1_fsm_create(void *ctx, struct v5x_link *v5l, uint8_t
 	if (!l1)
 		return NULL;
 	l1->v5l = v5l;
+	l1->sa7 = -1;
 
 	l1->fi = osmo_fsm_inst_alloc(&v5x_l1_fsm, l1, l1, LOGL_DEBUG, NULL);
 	if (!l1->fi)
@@ -612,7 +613,7 @@ void v5x_l1_init(void)
 
 	rc = osmo_fsm_register(&v5x_l1_fsm);
 	OSMO_ASSERT(!rc);
-	LOGP(DV5PSTN, LOGL_NOTICE, "Using V5x L1 protocol\n");
+	LOGP(DV5L1, LOGL_NOTICE, "Using V5x L1 protocol\n");
 }
 
 
@@ -629,55 +630,64 @@ int v5x_l1_signal_rcv(struct v5x_link *v5l, enum l1_signal_prim prim)
 
 	switch (prim) {
 	case L1_SIGNAL_LOS:
+		LOGP(DV5L1, LOGL_DEBUG, "Signal LOS detected on link %d.\n", v5l->id);
 		if (!l1->los) {
 			l1->los = 1;
 			osmo_fsm_inst_dispatch(fi, V5X_L1FSM_E_LOS, NULL);
 		}
 		break;
 	case L1_SIGNAL_NO_LOS:
+		LOGP(DV5L1, LOGL_DEBUG, "Signal LOS gone on link %d.\n", v5l->id);
 		if (l1->los) {
 			l1->los = 0;
 			state_changed = 1;
 		}
 		break;
 	case L1_SIGNAL_RAI:
+		LOGP(DV5L1, LOGL_DEBUG, "Signal RAI detected on link %d.\n", v5l->id);
 		if (!l1->rai) {
 			l1->rai = 1;
 			osmo_fsm_inst_dispatch(fi, V5X_L1FSM_E_RAI, NULL);
 		}
 		break;
 	case L1_SIGNAL_NO_RAI:
+		LOGP(DV5L1, LOGL_DEBUG, "Signal RAI gone on link %d.\n", v5l->id);
 		if (l1->rai) {
 			l1->rai = 0;
 			state_changed = 1;
 		}
 		break;
 	case L1_SIGNAL_AIS:
+		LOGP(DV5L1, LOGL_DEBUG, "Signal AIS detected on link %d.\n", v5l->id);
 		if (!l1->ais) {
 			l1->ais = 1;
 			osmo_fsm_inst_dispatch(fi, V5X_L1FSM_E_AIS, NULL);
 		}
 		break;
 	case L1_SIGNAL_NO_AIS:
+		LOGP(DV5L1, LOGL_DEBUG, "Signal AIS gone on link %d.\n", v5l->id);
 		if (l1->ais) {
 			l1->ais = 0;
 			state_changed = 1;
 		}
 		break;
 	case L1_SIGNAL_SA7_0:
-		if (!l1->sa7_zero) {
-			l1->sa7_zero = 1;
+
+		if (l1->sa7 != 0) {
+			LOGP(DV5L1, LOGL_DEBUG, "Bit Sa7=0 on link %d.\n", v5l->id);
+			l1->sa7 = 0;
 			state_changed = 1;
 		}
 		break;
 	case L1_SIGNAL_SA7_1:
-		if (l1->sa7_zero) {
-			l1->sa7_zero = 0;
+		if (l1->sa7 != 1) {
+			LOGP(DV5L1, LOGL_DEBUG, "Bit Sa7=1 on link %d.\n", v5l->id);
+			l1->sa7 = 1;
 			state_changed = 1;
 		}
 		break;
 	default:
-		LOGP(DV5PSTN, LOGL_NOTICE, "Invalid L1 primitive %d receied from physical layer.\n", prim);
+		LOGP(DV5L1, LOGL_NOTICE, "Invalid L1 primitive %d receied from physical layer.\n", prim);
 		return -EINVAL;
 	}
 
@@ -685,7 +695,7 @@ int v5x_l1_signal_rcv(struct v5x_link *v5l, enum l1_signal_prim prim)
 	 * We must do this, because there is no frame reception to trigger this.
 	 */
 	if (state_changed && !l1->los && !l1->rai && !l1->ais) {
-		if (l1->sa7_zero)
+		if (l1->sa7 == 0)
 			osmo_fsm_inst_dispatch(fi, V5X_L1FSM_E_NORMAL_Sa7, NULL);
 		else
 			osmo_fsm_inst_dispatch(fi, V5X_L1FSM_E_NORMAL, NULL);