diff --git a/conf/vanilla/sip_profiles/internal.xml b/conf/vanilla/sip_profiles/internal.xml
index b8390c7934..b9605a192c 100644
--- a/conf/vanilla/sip_profiles/internal.xml
+++ b/conf/vanilla/sip_profiles/internal.xml
@@ -27,6 +27,11 @@
   </domains>
   
   <settings>
+
+
+    <!-- inject delay between dtmf digits on send to help some slow interpreters (also per channel with rtp_digit_delay var -->
+    <!-- <param name="rtp-digit-delay" value="40"/>-->
+
     <!--
 	When calls are in no media this will bring them back to media
 	when you press the hold button.
diff --git a/src/include/switch_rtp.h b/src/include/switch_rtp.h
index a61326a6b8..0951498c37 100644
--- a/src/include/switch_rtp.h
+++ b/src/include/switch_rtp.h
@@ -461,6 +461,7 @@ SWITCH_DECLARE(void) switch_rtp_intentional_bugs(switch_rtp_t *rtp_session, swit
 
 SWITCH_DECLARE(switch_rtp_stats_t *) switch_rtp_get_stats(switch_rtp_t *rtp_session, switch_memory_pool_t *pool);
 SWITCH_DECLARE(switch_byte_t) switch_rtp_check_auto_adj(switch_rtp_t *rtp_session);
+SWITCH_DECLARE(void) switch_rtp_set_interdigit_delay(switch_rtp_t *rtp_session, uint32_t delay);
 
 /*!
   \}
diff --git a/src/mod/endpoints/mod_sofia/mod_sofia.h b/src/mod/endpoints/mod_sofia/mod_sofia.h
index 69afee7c29..730b592187 100644
--- a/src/mod/endpoints/mod_sofia/mod_sofia.h
+++ b/src/mod/endpoints/mod_sofia/mod_sofia.h
@@ -668,6 +668,7 @@ struct sofia_profile {
 	uint32_t sip_expires_max_deviation;
 	int ireg_seconds;
 	sofia_paid_type_t paid_type;
+	uint32_t rtp_digit_delay;
 };
 
 struct private_object {
diff --git a/src/mod/endpoints/mod_sofia/sofia.c b/src/mod/endpoints/mod_sofia/sofia.c
index 921708c4e3..44afd6242d 100644
--- a/src/mod/endpoints/mod_sofia/sofia.c
+++ b/src/mod/endpoints/mod_sofia/sofia.c
@@ -2957,6 +2957,12 @@ switch_status_t reconfig_sofia(sofia_profile_t *profile)
 						} else {
 							sofia_clear_pflag(profile, PFLAG_PASS_CALLEE_ID);
 						}
+					} else if (!strcasecmp(var, "rtp-digit-timeout")) {
+						int delay = val ? atoi(val) : 0;
+						
+						if (delay < 0) delay = 0;
+
+						profile->rtp_digit_delay = (uint32_t) delay;
 					} else if (!strcasecmp(var, "watchdog-enabled")) {
 						profile->watchdog_enabled = switch_true(val);
 					} else if (!strcasecmp(var, "watchdog-step-timeout")) {
@@ -3839,6 +3845,13 @@ switch_status_t config_sofia(int reload, char *profile_name)
 						} else {
 							sofia_clear_pflag(profile, PFLAG_LIBERAL_DTMF);
 						}
+					} else if (!strcasecmp(var, "rtp-digit-timeout")) {
+						int delay = val ? atoi(val) : 0;
+						
+						if (delay < 0) delay = 0;
+
+						profile->rtp_digit_delay = (uint32_t) delay;
+						
 					} else if (!strcasecmp(var, "watchdog-enabled")) {
 						profile->watchdog_enabled = switch_true(val);
 					} else if (!strcasecmp(var, "watchdog-step-timeout")) {
diff --git a/src/mod/endpoints/mod_sofia/sofia_glue.c b/src/mod/endpoints/mod_sofia/sofia_glue.c
index 645203520f..871c433090 100644
--- a/src/mod/endpoints/mod_sofia/sofia_glue.c
+++ b/src/mod/endpoints/mod_sofia/sofia_glue.c
@@ -3532,6 +3532,21 @@ switch_status_t sofia_glue_activate_rtp(private_object_t *tech_pvt, switch_rtp_f
 			tech_pvt->cng_pt = 0;
 		}
 
+		if (tech_pvt->profile->rtp_digit_delay || ((val = switch_channel_get_variable(tech_pvt->channel, "rtp_digit_delay")))) {
+			uint32_t delay = tech_pvt->profile->rtp_digit_delay;
+
+			if (!delay) {
+				int delayi = atoi(val);
+				if (delayi < 0) delayi = 0;
+				delay = (uint32_t) delay;
+			}
+
+			switch_rtp_set_interdigit_delay(tech_pvt->rtp_session, delay);
+			switch_log_printf(SWITCH_CHANNEL_SESSION_LOG(tech_pvt->session), SWITCH_LOG_DEBUG, 
+							  "%s Set rtp dtmf delay to %u\n", switch_channel_get_name(tech_pvt->channel), delay);
+			
+		}
+
 		if (tech_pvt->cng_pt && !sofia_test_pflag(tech_pvt->profile, PFLAG_SUPPRESS_CNG)) {
 			switch_log_printf(SWITCH_CHANNEL_SESSION_LOG(tech_pvt->session), SWITCH_LOG_DEBUG, "Set comfort noise payload to %u\n", tech_pvt->cng_pt);
 			switch_rtp_set_cng_pt(tech_pvt->rtp_session, tech_pvt->cng_pt);
diff --git a/src/switch_rtp.c b/src/switch_rtp.c
index fefb50f551..193520000f 100644
--- a/src/switch_rtp.c
+++ b/src/switch_rtp.c
@@ -193,6 +193,7 @@ struct switch_rtp {
 	uint32_t last_cng_ts;
 	uint32_t last_write_samplecount;
 	uint32_t delay_samples;
+	uint32_t next_write_samplecount;
 	uint32_t max_next_write_samplecount;
 	uint32_t queue_delay;
 	switch_time_t last_write_timestamp;
@@ -248,6 +249,15 @@ struct switch_rtp {
 	uint32_t sync_packets;
 	int rtcp_interval;
 	switch_bool_t rtcp_fresh_frame;
+
+	switch_time_t send_time;
+	switch_byte_t auto_adj_used;
+	uint8_t pause_jb;
+	uint16_t last_seq;
+	switch_time_t last_read_time;
+	switch_size_t last_flush_packet_count;
+	uint32_t interdigit_delay;
+
 #ifdef ENABLE_ZRTP
 	zrtp_session_t *zrtp_session;
 	zrtp_profile_t *zrtp_profile;
@@ -256,12 +266,7 @@ struct switch_rtp {
 	int zinit;
 #endif
 
-	switch_time_t send_time;
-	switch_byte_t auto_adj_used;
-	uint8_t pause_jb;
-	uint16_t last_seq;
-	switch_time_t last_read_time;
-	switch_size_t last_flush_packet_count;
+
 };
 
 struct switch_rtcp_senderinfo {
@@ -2223,6 +2228,11 @@ SWITCH_DECLARE(void) switch_rtp_destroy(switch_rtp_t **rtp_session)
 	return;
 }
 
+SWITCH_DECLARE(void) switch_rtp_set_interdigit_delay(switch_rtp_t *rtp_session, uint32_t delay) 
+{
+	rtp_session->interdigit_delay = delay;
+}
+
 SWITCH_DECLARE(switch_socket_t *) switch_rtp_get_rtp_socket(switch_rtp_t *rtp_session)
 {
 	return rtp_session->sock_input;
@@ -2289,6 +2299,7 @@ static void set_dtmf_delay(switch_rtp_t *rtp_session, uint32_t ms, uint32_t max_
 
 	if (switch_test_flag(rtp_session, SWITCH_RTP_FLAG_USE_TIMER)) {
 		rtp_session->max_next_write_samplecount = rtp_session->timer.samplecount + max_upsamp;
+		rtp_session->next_write_samplecount = rtp_session->timer.samplecount + upsamp;
 	}
 
 	switch_log_printf(SWITCH_CHANNEL_SESSION_LOG(session), SWITCH_LOG_DEBUG, "Queue digit delay of %dms\n", ms);	
@@ -2359,7 +2370,11 @@ static void do_2833(switch_rtp_t *rtp_session, switch_core_session_t *session)
 			}
 
 			rtp_session->dtmf_data.out_digit_dur = 0;
-			set_dtmf_delay(rtp_session, 40, 500);
+
+			if (rtp_session->interdigit_delay) {
+				set_dtmf_delay(rtp_session, rtp_session->interdigit_delay, rtp_session->interdigit_delay * 10);
+			}
+
 			return;
 		}
 	}
@@ -2368,7 +2383,7 @@ static void do_2833(switch_rtp_t *rtp_session, switch_core_session_t *session)
 		void *pop;
 
 		if (switch_test_flag(rtp_session, SWITCH_RTP_FLAG_USE_TIMER)) {
-			if (rtp_session->timer.samplecount < rtp_session->max_next_write_samplecount) {
+			if (rtp_session->timer.samplecount < rtp_session->next_write_samplecount) {
 				return;
 			}