diff --git a/libs/freetdm/mod_freetdm/mod_freetdm.c b/libs/freetdm/mod_freetdm/mod_freetdm.c
index 890d9d9d43..0117fcedf1 100755
--- a/libs/freetdm/mod_freetdm/mod_freetdm.c
+++ b/libs/freetdm/mod_freetdm/mod_freetdm.c
@@ -40,7 +40,7 @@
 
 #define FREETDM_LIMIT_REALM "__freetdm"
 #define FREETDM_VAR_PREFIX "freetdm_"
-#define FREETDM_VAR_PREFIX_LEN 8
+#define FREETDM_VAR_PREFIX_LEN (sizeof(FREETDM_VAR_PREFIX)-1) 
 
 SWITCH_MODULE_LOAD_FUNCTION(mod_freetdm_load);
 SWITCH_MODULE_SHUTDOWN_FUNCTION(mod_freetdm_shutdown);
@@ -1302,11 +1302,14 @@ static switch_call_cause_t channel_outgoing_channel(switch_core_session_t *sessi
 		}
 	}
 
-	ftdm_channel_clear_vars(ftdmchan);
+	span_id = ftdm_channel_get_span_id(ftdmchan);
+	chan_id = ftdm_channel_get_id(ftdmchan);
+
 	for (h = var_event->headers; h; h = h->next) {
 		if (!strncasecmp(h->name, FREETDM_VAR_PREFIX, FREETDM_VAR_PREFIX_LEN)) {
 			char *v = h->name + FREETDM_VAR_PREFIX_LEN;
 			if (!zstr(v)) {
+				switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_DEBUG, "Adding outbound freetdm variable %s=%s to channel %d:%d\n", v, h->value, span_id, chan_id);
 				ftdm_channel_add_var(ftdmchan, v, h->value);
 			}
 		}
@@ -1317,9 +1320,6 @@ static switch_call_cause_t channel_outgoing_channel(switch_core_session_t *sessi
 		switch_caller_profile_t *caller_profile;
 		switch_channel_t *channel = switch_core_session_get_channel(*new_session);
 		
-		span_id = ftdm_channel_get_span_id(ftdmchan);
-		chan_id = ftdm_channel_get_id(ftdmchan);
-
 		switch_core_session_add_stream(*new_session, NULL);
 		if ((tech_pvt = (private_t *) switch_core_session_alloc(*new_session, sizeof(private_t))) != 0) {
 			tech_init(tech_pvt, *new_session, ftdmchan);
@@ -1403,6 +1403,9 @@ ftdm_status_t ftdm_channel_from_event(ftdm_sigmsg_t *sigmsg, switch_core_session
 	switch_core_session_t *session = NULL;
 	private_t *tech_pvt = NULL;
 	switch_channel_t *channel = NULL;
+	ftdm_iterator_t *iter = NULL;
+	const char *var_name = NULL;
+	const char *var_value = NULL;
 	uint32_t spanid, chanid;
 	char name[128];
 	ftdm_caller_data_t *channel_caller_data = ftdm_channel_get_caller_data(sigmsg->channel);
@@ -1511,6 +1514,13 @@ ftdm_status_t ftdm_channel_from_event(ftdm_sigmsg_t *sigmsg, switch_core_session
 	if (channel_caller_data->raw_data_len) {
 		switch_channel_set_variable_printf(channel, "freetdm_custom_call_data", "%s", channel_caller_data->raw_data);
 	}
+	/* Add any channel variable to the dial plan */
+	iter = ftdm_channel_get_var_iterator(sigmsg->channel);
+	for ( ; iter; iter = ftdm_iterator_next(iter)) {
+		ftdm_channel_get_current_var(iter, &var_name, &var_value);
+		snprintf(name, sizeof(name), FREETDM_VAR_PREFIX "%s", var_name);
+		switch_channel_set_variable_printf(channel, name, "%s", var_value);
+	}
 		
 	switch_channel_set_state(channel, CS_INIT);
 	if (switch_core_session_thread_launch(session) != SWITCH_STATUS_SUCCESS) {
diff --git a/libs/freetdm/src/ftdm_io.c b/libs/freetdm/src/ftdm_io.c
index 238a9fc060..b087881e1d 100644
--- a/libs/freetdm/src/ftdm_io.c
+++ b/libs/freetdm/src/ftdm_io.c
@@ -400,8 +400,6 @@ static ftdm_status_t ftdm_channel_destroy(ftdm_channel_t *ftdmchan)
 		ftdm_buffer_destroy(&ftdmchan->fsk_buffer);
 		ftdmchan->pre_buffer_size = 0;
 
-		hashtable_destroy(ftdmchan->variable_hash);
-
 		ftdm_safe_free(ftdmchan->dtmf_hangup_buf);
 
 		if (ftdmchan->tone_session.buffer) {
@@ -812,7 +810,6 @@ FT_DECLARE(ftdm_status_t) ftdm_span_add_channel(ftdm_span_t *span, ftdm_socket_t
 
 		ftdm_buffer_create(&new_chan->digit_buffer, 128, 128, 0);
 		ftdm_buffer_create(&new_chan->gen_dtmf_buffer, 128, 128, 0);
-		new_chan->variable_hash = create_hashtable(16, ftdm_hash_hashfromstring, ftdm_hash_equalkeys);
 
 		new_chan->dtmf_hangup_buf = ftdm_calloc (span->dtmf_hangup_len + 1, sizeof (char));
 
@@ -2213,9 +2210,10 @@ static void close_dtmf_debug(ftdm_channel_t *ftdmchan)
 }
 #endif
 
+static ftdm_status_t ftdm_channel_clear_vars(ftdm_channel_t *ftdmchan);
 FT_DECLARE(ftdm_status_t) ftdm_channel_done(ftdm_channel_t *ftdmchan)
 {
-	assert(ftdmchan != NULL);
+	ftdm_assert_return(ftdmchan != NULL, FTDM_FAIL, "Null channel can't be done!\n");
 
 	ftdm_mutex_lock(ftdmchan->mutex);
 
@@ -2243,6 +2241,7 @@ FT_DECLARE(ftdm_status_t) ftdm_channel_done(ftdm_channel_t *ftdmchan)
 #ifdef FTDM_DEBUG_DTMF
 	close_dtmf_debug(ftdmchan);
 #endif
+	ftdm_channel_clear_vars(ftdmchan);
 
 	ftdmchan->init_state = FTDM_CHANNEL_STATE_DOWN;
 	ftdmchan->state = FTDM_CHANNEL_STATE_DOWN;
@@ -3368,8 +3367,8 @@ FT_DECLARE(ftdm_status_t) ftdm_channel_write(ftdm_channel_t *ftdmchan, void *dat
 	ftdm_size_t max = datasize;
 	unsigned int i = 0;
 
-	assert(ftdmchan != NULL);
-	assert(ftdmchan->fio != NULL);
+	ftdm_assert_return(ftdmchan != NULL, FTDM_FAIL, "null channel on write!\n");
+	ftdm_assert_return(ftdmchan->fio != NULL, FTDM_FAIL, "null I/O on write!\n");
 
 	if (!ftdmchan->buffer_delay && 
 		((ftdmchan->dtmf_buffer && ftdm_buffer_inuse(ftdmchan->dtmf_buffer)) ||
@@ -3421,16 +3420,16 @@ FT_DECLARE(ftdm_status_t) ftdm_channel_write(ftdm_channel_t *ftdmchan, void *dat
 	return status;
 }
 
-FT_DECLARE(ftdm_status_t) ftdm_channel_clear_vars(ftdm_channel_t *ftdmchan)
+static ftdm_status_t ftdm_channel_clear_vars(ftdm_channel_t *ftdmchan)
 {
-	if(ftdmchan->variable_hash) {
+	ftdm_channel_lock(ftdmchan);
+
+	if (ftdmchan->variable_hash) {
 		hashtable_destroy(ftdmchan->variable_hash);
 	}
-	ftdmchan->variable_hash = create_hashtable(16, ftdm_hash_hashfromstring, ftdm_hash_equalkeys);
+	ftdmchan->variable_hash = NULL;
 
-	if(!ftdmchan->variable_hash)
-		return FTDM_FAIL;
-	
+	ftdm_channel_unlock(ftdmchan);
 	return FTDM_SUCCESS;
 }
 
@@ -3438,34 +3437,98 @@ FT_DECLARE(ftdm_status_t) ftdm_channel_add_var(ftdm_channel_t *ftdmchan, const c
 {
 	char *t_name = 0, *t_val = 0;
 
-	if(!ftdmchan->variable_hash || !var_name || !value)
-	{
+	ftdm_status_t status = FTDM_FAIL;
+
+	if (!var_name || !value) {
 		return FTDM_FAIL;
 	}
 
+	ftdm_channel_lock(ftdmchan);
+
+	if (!ftdmchan->variable_hash) {
+		/* initialize on first use */
+		ftdmchan->variable_hash = create_hashtable(16, ftdm_hash_hashfromstring, ftdm_hash_equalkeys);
+		if (!ftdmchan->variable_hash) {
+			goto done;
+		}
+	}
+
 	t_name = ftdm_strdup(var_name);
 	t_val = ftdm_strdup(value);
 
-	if(hashtable_insert(ftdmchan->variable_hash, t_name, t_val, HASHTABLE_FLAG_FREE_KEY | HASHTABLE_FLAG_FREE_VALUE)) {
-		return FTDM_SUCCESS;
-	}
-	return FTDM_FAIL;
+	hashtable_insert(ftdmchan->variable_hash, t_name, t_val, HASHTABLE_FLAG_FREE_KEY | HASHTABLE_FLAG_FREE_VALUE);
+
+	status = FTDM_SUCCESS;
+
+done:
+	ftdm_channel_unlock(ftdmchan);
+
+	return status;
 }
 
 FT_DECLARE(const char *) ftdm_channel_get_var(ftdm_channel_t *ftdmchan, const char *var_name)
 {
-	if(!ftdmchan->variable_hash || !var_name)
-	{
+	const char *var = NULL;
+
+	ftdm_channel_lock(ftdmchan);
+
+	if (!ftdmchan->variable_hash || !var_name) {
+		goto done;
+	}
+	
+	var = (const char *)hashtable_search(ftdmchan->variable_hash, (void *)var_name);
+
+done:
+	ftdm_channel_unlock(ftdmchan);
+
+	return var;
+}
+
+FT_DECLARE(ftdm_iterator_t *) ftdm_channel_get_var_iterator(const ftdm_channel_t *ftdmchan)
+{
+	ftdm_hash_iterator_t *iter = NULL;
+
+	ftdm_channel_lock(ftdmchan);
+
+	iter = ftdmchan->variable_hash == NULL ? NULL : hashtable_first(ftdmchan->variable_hash);
+
+	ftdm_channel_unlock(ftdmchan);
+
+	return iter;
+}
+
+FT_DECLARE(ftdm_status_t) ftdm_channel_get_current_var(ftdm_iterator_t *iter, const char **var_name, const char **var_val)
+{
+	const void *key = NULL;
+	void *val = NULL;
+
+	*var_name = NULL;
+	*var_val = NULL;
+
+	if (!iter) {
+		return FTDM_FAIL;
+	}
+
+	hashtable_this(iter, &key, NULL, &val);
+
+	*var_name = key;
+	*var_val = val;
+
+	return FTDM_SUCCESS;
+}
+
+FT_DECLARE(ftdm_iterator_t *) ftdm_iterator_next(ftdm_iterator_t *iter)
+{
+	if (!iter) {
 		return NULL;
 	}
-	return (const char *) hashtable_search(ftdmchan->variable_hash, (void *)var_name);
+	return hashtable_next(iter);
 }
 
 static struct {
 	ftdm_io_interface_t *pika_interface;
 } interfaces;
 
-
 FT_DECLARE(char *) ftdm_api_execute(const char *cmd)
 {
 	ftdm_io_interface_t *fio = NULL;
diff --git a/libs/freetdm/src/ftmod/ftmod_sangoma_isdn/ftmod_sangoma_isdn.c b/libs/freetdm/src/ftmod/ftmod_sangoma_isdn/ftmod_sangoma_isdn.c
index b47660b076..a98429da73 100644
--- a/libs/freetdm/src/ftmod/ftmod_sangoma_isdn/ftmod_sangoma_isdn.c
+++ b/libs/freetdm/src/ftmod/ftmod_sangoma_isdn/ftmod_sangoma_isdn.c
@@ -35,7 +35,6 @@
 
 
 #include "ftmod_sangoma_isdn.h"
-#define FTDM_DEBUG_CHAN_MEMORY
 
 #ifdef FTDM_DEBUG_CHAN_MEMORY
 #include <sys/mman.h>
@@ -472,7 +471,10 @@ static void ftdm_sangoma_isdn_process_state_change(ftdm_channel_t *ftdmchan)
 	case FTDM_CHANNEL_STATE_RING: /* incoming call request */
 		{
 			ftdm_log_chan(ftdmchan, FTDM_LOG_DEBUG, "Sending incoming call from %s to %s to FTDM core\n", ftdmchan->caller_data.ani.digits, ftdmchan->caller_data.dnis.digits);
-
+			ftdm_channel_add_var(ftdmchan, "isdn_specific_var", "1");
+			ftdm_channel_add_var(ftdmchan, "isdn_crap", "morecrap");
+			ftdm_channel_add_var(ftdmchan, "isdn_stuff", "s");
+			ftdm_channel_add_var(ftdmchan, "isdn_d", "asdsadasdasdsad");
 			/* we have enough information to inform FTDM of the call*/
 			sigev.event_id = FTDM_SIGEVENT_START;
 			ftdm_span_send_signal(ftdmchan->span, &sigev);
diff --git a/libs/freetdm/src/include/freetdm.h b/libs/freetdm/src/include/freetdm.h
index 132fd303a2..61d37c8878 100644
--- a/libs/freetdm/src/include/freetdm.h
+++ b/libs/freetdm/src/include/freetdm.h
@@ -381,6 +381,9 @@ typedef struct ftdm_conf_parameter {
 	void *ptr;
 } ftdm_conf_parameter_t;
 
+/*! \brief Opaque general purpose iterator */
+typedef void ftdm_iterator_t;
+
 /*! \brief Channel commands that can be executed through ftdm_channel_command() */
 typedef enum {
 	FTDM_COMMAND_NOOP,
@@ -1014,14 +1017,25 @@ FT_DECLARE(ftdm_status_t) ftdm_channel_read(ftdm_channel_t *ftdmchan, void *data
  */
 FT_DECLARE(ftdm_status_t) ftdm_channel_write(ftdm_channel_t *ftdmchan, void *data, ftdm_size_t datasize, ftdm_size_t *datalen);
 
-/*! \brief Add a custom variable to the channel */
+/*! \brief Add a custom variable to the channel
+ *  \note This variables may be used by signaling modules to override signaling parameters
+ *  \todo Document which signaling variables are available
+ * */
 FT_DECLARE(ftdm_status_t) ftdm_channel_add_var(ftdm_channel_t *ftdmchan, const char *var_name, const char *value);
 
-/*! \brief Get a custom variable from the channel */
+/*! \brief Get a custom variable from the channel. 
+ *  \note The variable pointer returned is only valid while the channel is open and it'll be destroyed when the channel is closed. */
 FT_DECLARE(const char *) ftdm_channel_get_var(ftdm_channel_t *ftdmchan, const char *var_name);
 
-/*! \brief Clear custom channel variables from the channel */
-FT_DECLARE(ftdm_status_t) ftdm_channel_clear_vars(ftdm_channel_t *ftdmchan);
+/*! \brief Get an iterator to iterate over the channel variables
+ *  \note The iterator pointer returned is only valid while the channel is open and it'll be destroyed when the channel is closed. */
+FT_DECLARE(ftdm_iterator_t *) ftdm_channel_get_var_iterator(const ftdm_channel_t *ftdmchan);
+
+/*! \brief Get variable name and value for the current iterator position */
+FT_DECLARE(ftdm_status_t) ftdm_channel_get_current_var(ftdm_iterator_t *iter, const char **var_name, const char **var_val);
+
+/*! \brief Advance iterator */
+FT_DECLARE(ftdm_iterator_t *) ftdm_iterator_next(ftdm_iterator_t *iter);
 
 /*! \brief Get the span pointer associated to the channel */
 FT_DECLARE(ftdm_span_t *) ftdm_channel_get_span(const ftdm_channel_t *ftdmchan);
diff --git a/libs/freetdm/src/include/private/ftdm_core.h b/libs/freetdm/src/include/private/ftdm_core.h
index 95f34b4dd2..eb9a84a84a 100644
--- a/libs/freetdm/src/include/private/ftdm_core.h
+++ b/libs/freetdm/src/include/private/ftdm_core.h
@@ -579,7 +579,6 @@ FT_DECLARE(ftdm_status_t) ftdm_span_next_event(ftdm_span_t *span, ftdm_event_t *
  */
 FT_DECLARE(ftdm_status_t) ftdm_channel_queue_dtmf(ftdm_channel_t *ftdmchan, const char *dtmf);
 
-
 /*!
   \brief Assert condition
 */