Play announcement to called party - problem

I am having a problem with play announcement to called party. It works fine with SIP extensions but not with ZAP ones. When I monitor what is happening, it appears to be playing to the called extension but the called extension hears nothing.

My zapata.conf has the following lines:

language=en
musiconhold=default
relaxdtmf=yes
callwaiting=yes
callwaitingcallerid=yes
threewaycalling=yes
transfer=yes
cancallforward=yes
usecallerid=yes
echocancel=yes
echocancelwhenbridged=yes
rxgain=0.0
txgain=0.0
immediate=no
callerid=asreceived
signalling=fxs_ks
context=from-ptsn
channel=1

Zaptel.conf has only 3 lines:

loadzone = uk
defaultzone=uk
fxsks=1

Can anyone throw any light on th esubject?

Steven

Since my last message I have been looking carefully at the console to see what Asterisk actually does.

My Zap channel is a trunk connection. It seems that when Asterisk Dials the Zap interface this counts as an aswer and the message is played to the called party (ie the Zap channel) before the person who is being called on teh trunk line picks up.

Can anyone suggest how I can get round this and send an announcement to the called trunk party once they have picked up?

Thanks.

Steven