diff --git a/conf.d/ysigchan.conf.sample b/conf.d/ysigchan.conf.sample
index b9821317..4282fb2a 100644
--- a/conf.d/ysigchan.conf.sample
+++ b/conf.d/ysigchan.conf.sample
@@ -134,10 +134,10 @@
 ; Defaults to user-provided if missing or incorrect
 ;screening=user-provided
 
-; format: string:  Default data format for outgoing calls. Values: alaw, mulaw, g721
-; Defaults to alaw if missing or incorrect
+; format: string: Default data format for outgoing calls. Values: alaw, mulaw, g721
+; Defaults to mulaw for ANSI and Japan point codes, alaw for all others
 ; alaw is used commonly in Europe while mulaw is used commonly in US and Japan.
-;format=alaw
+;format=
 
 ; print-messages: boolean: Print decoded protocol data units to output
 ; This option is applied on reload
diff --git a/libs/ysig/isup.cpp b/libs/ysig/isup.cpp
index c60a79b4..a4368c34 100644
--- a/libs/ysig/isup.cpp
+++ b/libs/ysig/isup.cpp
@@ -2254,7 +2254,16 @@ SS7ISUP::SS7ISUP(const NamedList& params)
 
     m_format = params.getValue("format");
     if (-1 == lookup(m_format,SignallingUtils::dict(0,0),-1))
-	m_format = "alaw";
+	switch (m_type) {
+	    case SS7PointCode::ANSI:
+	    case SS7PointCode::ANSI8:
+	    case SS7PointCode::Japan:
+	    case SS7PointCode::Japan5:
+		m_format = "mulaw";
+		break;
+	    default:
+		m_format = "alaw";
+	}
 
     const char* rpc = params.getValue("remotepointcode");
     m_remotePoint = new SS7PointCode(0,0,0);