diff --git a/libs/openzap/src/isdn/Q921.c b/libs/openzap/src/isdn/Q921.c
index 9eab78b99e..956a9e180c 100644
--- a/libs/openzap/src/isdn/Q921.c
+++ b/libs/openzap/src/isdn/Q921.c
@@ -259,6 +259,15 @@ int Q921SendSABME(L2TRUNK trunk, int Sapi, int cr, int Tei, int pf)
     return Q921Tx21Proc(trunk, mes, trunk->Q921HeaderSpace+3);
 }
 
+int Q921Start(L2TRUNK trunk)
+{
+	return Q921SendSABME(trunk, 
+					trunk->sapi, 
+					trunk->NetUser == Q921_TE ? 0 : 1,
+					trunk->tei, 
+					0);
+}
+
 /*****************************************************************************
 
   Function:     Q921SendDM
diff --git a/libs/openzap/src/isdn/include/Q921.h b/libs/openzap/src/isdn/include/Q921.h
index 9338a49c99..4acdf8ece9 100644
--- a/libs/openzap/src/isdn/include/Q921.h
+++ b/libs/openzap/src/isdn/include/Q921.h
@@ -124,5 +124,6 @@ void Q921_InitTrunk(L2TRUNK trunk,
 int Q921QueueHDLCFrame(L2TRUNK trunk, L2UCHAR *b, L2INT size);
 int Q921Rx12(L2TRUNK trunk);
 int Q921Rx32(L2TRUNK trunk, L2UCHAR * Mes, L2INT Size);
+int Q921Start(L2TRUNK trunk);
 #endif