asterisk users - May 2006 - Asterisk auto-dial out: behaviour difference between analog and ISDN channel

Hi,
I have an Asterisk 1.2.1 box on a Debian Sarge with a TDM400P and a 
beronet monoBRI ISDN card.
I need to make an auto-dial out call and I have two choices: use an 
analog channel or an ISDN channel.
When I make an auto-dial out call using an analog channel, Asterisk 
makes the calling phone ring while trying to connect to the  other 
party: this is the behaviour I want, so the caller knows  his/her phone 
is trying to call.
When I do the same using an ISDN channel, Asterisk does not make the 
caller phone ring, so the caller does not know the phone is calling.

Is there anybody who experienced this problem and solved it?

TIA

Giorgio Incantalupo

P.S.: I paste my mISDN.conf here if it can help:

*[general]
debug = 0
tracefile = /var/log/asterisk/misdn.trace
trace_calls = false
trace_dir = /var/log/asterisk/misdn
bridging = yes
stop_tone_after_first_digit = yes
append_digits2exten = yes
l1_info_ok = yes
clear_l3 = no
method = standard

;;; CRYPTION STUFF
dynamic_crypt = no
crypt_prefix = **
crypt_keys = test,muh

[default]
context = misdn
language = us
nationalprefix = 0
internationalprefix = 00
rxgain = 0
txgain = 0
te_choose_channel = no
dialplan = 0
use_callingpres = yes
echocancelwhenbridged = no
echotraining = yes

; inbound group
[inbound]
ports = 1,2,3,4
context = outbound_isdn*