diff --git a/library/RTP_Emulation.ttcn b/library/RTP_Emulation.ttcn
index 10cf683..e55890e 100644
--- a/library/RTP_Emulation.ttcn
+++ b/library/RTP_Emulation.ttcn
@@ -32,10 +32,7 @@
 	port RTPEM_CTRL_PT CTRL;
 
 	/* configurable by user, should be fixed */
-	var INT7b g_tx_payload_type := 0;
-	var integer g_tx_samplerate_hz := 8000;
-	var integer g_tx_duration_ms := 20;
-	var BIT32_BO_LAST g_tx_ssrc := hex2bit('DEADBEEF'H);
+	var RtpemConfig g_cfg := c_default_cfg;
 
 	var HostName g_remote_host;
 	var PortNumber g_remote_port;
@@ -59,12 +56,29 @@
 	RTPEM_MODE_BIDIR
 };
 
+type record RtpemConfig {
+	INT7b tx_payload_type,
+	integer tx_samplerate_hz,
+	integer tx_duration_ms,
+	BIT32_BO_LAST tx_ssrc,
+	octetstring tx_fixed_payload optional
+};
+
+const RtpemConfig c_default_cfg := {
+	tx_payload_type := 0,
+	tx_samplerate_hz := 8000,
+	tx_duration_ms := 20,
+	tx_ssrc := '11011110101011011011111011101111'B,
+	tx_fixed_payload := '01020304'O
+}
+
 signature RTPEM_bind(in HostName local_host, inout PortNumber local_port);
 signature RTPEM_connect(in HostName remote_host, in PortNumber remote_port);
 signature RTPEM_mode(in RtpemMode mode);
+signature RTPEM_configure(in RtpemConfig cfg);
 
 type port RTPEM_CTRL_PT procedure {
-	inout RTPEM_bind, RTPEM_connect, RTPEM_mode;
+	inout RTPEM_bind, RTPEM_connect, RTPEM_mode, RTPEM_configure;
 } with { extension "internal" };
 
 template PDU_RTP ts_RTP(BIT32_BO_LAST ssrc, INT7b pt, LIN2_BO_LAST seq, uint32_t ts,
@@ -84,20 +98,21 @@
 }
 
 private function f_tx_rtp(octetstring payload, BIT1 marker := '0'B) runs on RTP_Emulation_CT {
-	var PDU_RTP rtp := valueof(ts_RTP(g_tx_ssrc, g_tx_payload_type, g_tx_next_seq,
+	var PDU_RTP rtp := valueof(ts_RTP(g_cfg.tx_ssrc, g_cfg.tx_payload_type, g_tx_next_seq,
 					  g_tx_next_ts, payload, marker));
 	RTP.send(t_RTP_Send(g_rtp_conn_id, RTP_messages_union:{rtp:=rtp}));
 	/* increment sequence + timestamp for next transmit */
 	g_tx_next_seq := g_tx_next_seq + 1;
-	g_tx_next_ts := g_tx_next_ts + (g_tx_samplerate_hz / (1000 / g_tx_duration_ms));
+	g_tx_next_ts := g_tx_next_ts + (g_cfg.tx_samplerate_hz / (1000 / g_cfg.tx_duration_ms));
 }
 
 function f_main() runs on RTP_Emulation_CT
 {
 	var Result res;
 
-	timer T_transmit := int2float(g_tx_duration_ms)/1000.0;
+	timer T_transmit := int2float(g_cfg.tx_duration_ms)/1000.0;
 	var RTP_RecvFrom rx_rtp;
+	var RtpemConfig cfg;
 	var template RTP_RecvFrom tr := {
 		connId := ?,
 		remName := ?,
@@ -174,6 +189,9 @@
 				g_rx_enabled := true;
 			}
 		}
+		[] CTRL.getcall(RTPEM_configure:{?}) -> param (cfg) {
+			g_cfg := cfg;
+		}
 
 		/* simply ignore any RTTP/RTCP if receiver not enabled */
 		[g_rx_enabled==false] RTP.receive(tr_rtp) { }
@@ -190,7 +208,7 @@
 		/* transmit if timer has expired */
 		[] T_transmit.timeout {
 			/* send one RTP frame, re-start timer */
-			f_tx_rtp('01020304'O);
+			f_tx_rtp(g_cfg.tx_fixed_payload);
 			T_transmit.start;
 		}