Problem in Playing sound file to called party?

Hi all,

I have one query that if I want one audio file to be played to called party then what should I do in asterisk dialplan.

If I have two users at asterisk i.e 789 and 123.
If 789 user makes call to 123, then I want asterisk should play a sound file when 123 accepts the call.

I wrote these lines in dialplan for 123 :

exten => 123,1,System(echo ‘testing asterisk server for speech’ | /usr/bin/text2wave -scale 1.5 -F 8000 -o /home/test_asterisk.ulaw -otype ulaw)
exten => 123,2,Playback(/home/test_asterisk)

so when i call 123,
this sound file gets created and gets played to 789.
but i want this file to get played to called party, 123.

How should i do this?
what changes required in dialplan?

Please help.