[asterisk-users] {s} - extension

[Daniel Suleyman]

Dear all, I have small question

in sip.conf I added

[service]
type=friend
;username=
;secret=
qualify=900
host=X.X.X.X
dtmfmode = rfc2833
disallow=all
;allow=g729
allow=gsm
allow=alaw
allow=ulaw

and  I can proccess incoming call from soft phone only I calling on
number that is used in extensions.conf(in example below it is 1)

exten => 1,1,Answer;
exten => 1,2,Playback(hello-world,skip);
exten => 1,3,Hangup;

but when I use next construction(As I understand it is used to allow
to process any extension dialed by user)

exten => s,1,Answer;
exten => s,2,Playback(hello-world,skip);
exten => s,3,Hangup;

Asterisk  says call rejected due to no extension.

What is wrong? any body can make spot lighter.

Thank in advance.