diff --git a/openbsc/src/libbsc/e1_config.c b/openbsc/src/libbsc/e1_config.c
index 803772b..f1962c7 100644
--- a/openbsc/src/libbsc/e1_config.c
+++ b/openbsc/src/libbsc/e1_config.c
@@ -63,15 +63,10 @@
 		return -ENOMEM;
 	}
 
-	switch (ts->pchan) {
-	case GSM_PCHAN_TCH_F:
-	case GSM_PCHAN_TCH_H:
+	if (ts_is_tch(ts)) {
 		e1_ts = &line->ts[e1_link->e1_ts-1];
 		e1inp_ts_config_trau(e1_ts, line, subch_cb);
 		subch_demux_activate(&e1_ts->trau.demux, e1_link->e1_ts_ss);
-		break;
-	default:
-		break;
 	}
 
 	return 0;
diff --git a/openbsc/src/libcommon/gsm_data_shared.c b/openbsc/src/libcommon/gsm_data_shared.c
index 371e479..4eea21e 100644
--- a/openbsc/src/libcommon/gsm_data_shared.c
+++ b/openbsc/src/libcommon/gsm_data_shared.c
@@ -747,3 +747,19 @@
 {
 	return subslots_per_pchan[ts_pchan(ts)];
 }
+
+static bool pchan_is_tch(enum gsm_phys_chan_config pchan)
+{
+	switch (pchan) {
+	case GSM_PCHAN_TCH_F:
+	case GSM_PCHAN_TCH_H:
+		return true;
+	default:
+		return false;
+	}
+}
+
+bool ts_is_tch(struct gsm_bts_trx_ts *ts)
+{
+	return pchan_is_tch(ts_pchan(ts));
+}