diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index 9935014..fa6ca0c 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -6705,35 +6705,6 @@
 /***********************************************************************
  * DTX Related (see GSM 05.08, section 8.3)
  ***********************************************************************/
-
-/* XXX These functions must be kept in sync with g_AllChannels defined on test_CT. */
-private function f_g_chan_is_tchf() runs on ConnHdlr return boolean {
-	return (g_chan_nr == valueof(ts_RslChanNr_Bm(1)) or
-		g_chan_nr == valueof(ts_RslChanNr_Bm(2)) or
-		g_chan_nr == valueof(ts_RslChanNr_Bm(3)) or
-		g_chan_nr == valueof(ts_RslChanNr_Bm(4)));
-}
-private function f_g_chan_is_tchh() runs on ConnHdlr return boolean {
-	return (g_chan_nr == valueof(ts_RslChanNr_Lm(5,0)) or
-		g_chan_nr == valueof(ts_RslChanNr_Lm(5,1)));
-}
-private function f_g_chan_is_sdcch4() runs on ConnHdlr return boolean {
-	return (g_chan_nr == valueof(ts_RslChanNr_SDCCH4(0,0)) or
-		g_chan_nr == valueof(ts_RslChanNr_SDCCH4(0,1)) or
-		g_chan_nr == valueof(ts_RslChanNr_SDCCH4(0,2)) or
-		g_chan_nr == valueof(ts_RslChanNr_SDCCH4(0,3)));
-}
-private function f_g_chan_is_sdcch8() runs on ConnHdlr return boolean {
-	return (g_chan_nr == valueof(ts_RslChanNr_SDCCH8(6,0)) or
-		g_chan_nr == valueof(ts_RslChanNr_SDCCH8(6,1)) or
-		g_chan_nr == valueof(ts_RslChanNr_SDCCH8(6,2)) or
-		g_chan_nr == valueof(ts_RslChanNr_SDCCH8(6,3)) or
-		g_chan_nr == valueof(ts_RslChanNr_SDCCH8(6,4)) or
-		g_chan_nr == valueof(ts_RslChanNr_SDCCH8(6,5)) or
-		g_chan_nr == valueof(ts_RslChanNr_SDCCH8(6,6)) or
-		g_chan_nr == valueof(ts_RslChanNr_SDCCH8(6,7)));
-}
-
 private function f_test_l2_fill_frames(boolean dtxd) runs on ConnHdlr {
 	var L1ctlDlMessage dl;
 	var octetstring l2_fill_frame := '0303012B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B2B'O;
@@ -6780,7 +6751,7 @@
 		}
 
 		if (dtxd) {
-			if (not f_g_chan_is_tchf()) {
+			if (not match(g_chan_nr, t_RslChanNr_Bm(?))) {
 				T.stop;
 				f_rsl_chan_deact();
 				f_L1CTL_DM_REL_REQ(L1CTL, g_chan_nr);
@@ -6832,20 +6803,19 @@
 			}
 			if (fn > first_fn + frame_dtx_tchf_mod) {
 				T.stop;
-				if (f_g_chan_is_tchf()) {
-					/* Without DTX we can expect 25 fill frames for every 104 frames.
-					 * (24 FACCH + 1 SACCH filling) */
-					 expected_fill_frames := 25;
-				} else if (f_g_chan_is_tchh()) {
-					/* We can expect 2 fill frames for every 104 frames. */
-					 expected_fill_frames := 2;
-				} else if (f_g_chan_is_sdcch4() or f_g_chan_is_sdcch8()) {
-					/* We can expect 5 fill frames for every 104 frames. */
-					 expected_fill_frames := 5;
-				} else {
-					f_rsl_chan_deact();
-					f_L1CTL_DM_REL_REQ(L1CTL, g_chan_nr);
-					Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, "Unknown channel type");
+
+				select (g_chan_nr) {
+				/* TCH/F: we expect 25 fill frames (24 FACCH + 1 SACCH) for every 104 frames. */
+				case (t_RslChanNr_Bm(?)) { expected_fill_frames := 25; }
+				/* TCH/H: we expect 2 fill frames for every 104 frames. */
+				case (t_RslChanNr_Lm(?, ?)) { expected_fill_frames := 2; }
+				/* SDCCH: we expect 5 fill frames for every 104 frames. */
+				case (t_RslChanNr_SDCCH4(?, ?)) { expected_fill_frames := 5; }
+				case (t_RslChanNr_SDCCH8(?, ?)) { expected_fill_frames := 5; }
+				case else {
+					/* This shall not happen, just to be sure */
+					Misc_Helpers.f_shutdown(__BFILE__, __LINE__);
+					}
 				}
 
 				f_rsl_chan_deact();