asterisk users - Jun 2005 - 3-way conference using zap channels -- how is it done?

My configuration is one TDM31B for internal subscribers and one AVM B1
v.4for incoming/outgoing calls.

How do I:

a) transfer a call to an internal subscriber
b) commence a 3-way conference (two internal - one external subscribers)

I've searched voip-info.org <http://voip-info.org> and google god but 
regarding to zap channels documentation is not clear, if any, especially 
about 3-way conference.

Thank you

-- 
Dimitris Kouimintzis
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