H323 to SIP

My telephone station work only with H323 protocol and I have in my office only IP telephone with SIP protocol. How can I convert H323 to SIP using Asterisk PBX software

actually i have the same problem so plz if anyone knows how to convert from H323 to SIP and vice versa plesae inform me

Asterisk can switch these calls.

www.asterisk.org
debianhelp.co.uk/asterisk.htm
voip-info.org/wiki/view/Asterisk+FreeBSD