How to set PIN in confbridge() appl'n in asrk-1.8.8.0?

hi,

1.Im not geting any sound prompt from phone/device when entering PIN/password for entering into the conference.

exten => *100,1,Answer()
exten => *100,n,Confbridge(*100,Msc,1234)

asterisk version:1.8.8.0(im not installing DAHDI)

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