[Asterisk-Users] disable second call / call waiting via SIP

[Vladyslav]

HI!
I have a problem with Sjphone on ipaq.
It freeze when I receive a call on second line (seems like CPU is not
enough). It there a way to restrict call accepting when I'm already on
the phone via SIP in *?

because:
http://www.voip-info.org/wiki-PBX+Call+Waiting
For most POTS providers in the United States, Call Waiting may be turned
off by dialing *70 before dialing the telephone number.

Is there the same in * ?

Many thanks in advance.
-- 
Best regards
Vlad