[Asterisk-Users] Dialplan question - doesn't quite work

[DB]

Hi - I have a zaptel card with 4 modules - 2 fxs and two fxo. I have two
phone lines coming into my house.

For now I want an incoming call to ring a phone here, and then if no
answer to ring another number (by calling out on the other line) for 15
seconds... then if no answer send to voicemail. It seems to work, except
the last part... the outgoing call doesn't time out... if not answered
it will ring for eternity.

exten => s,1,Answer
exten => s,2,playback(thx4call)
exten => s,3,Dial(Zap/1|15,t) ; Calls  channel 1
exten => s,4,playback(trying_bert)
exten => s,5,Dial(Zap/4/12168810880|15,r)
exten => s,6,Voicemail,u100
exten => s,7,hangup
exten => s,104,Voicemail,b100
exten => s,105,hangup
exten => s,106,Voicemail,u100
exten =? s,107,hangup

I am a newbie but have done lots of reading and playing around. ANy
advice is welcome.

DB