diff --git a/configs/chan_dahdi.conf.sample b/configs/chan_dahdi.conf.sample
index 1f3f2ba93e..f69a111ca5 100644
--- a/configs/chan_dahdi.conf.sample
+++ b/configs/chan_dahdi.conf.sample
@@ -160,6 +160,11 @@
 ; Overlap dialing mode (sending overlap digits)
 ; Cannot be changed on a reload.
 ;
+; incoming: incoming direction only
+; outgoing: outgoing direction only
+; no: neither direction
+; yes or both: both directions
+;
 ;overlapdial=yes
 ;
 ; Allow inband audio (progress) when a call is RELEASEd by the far end of a PRI