[asterisk-users] connecting internal line with external line

[Ekkard Gerlach]

Hi, 

I'm new to asterisk. I want asterisk to connect a external line with 
an internal line: the PC dials a number and connects this call to a 
internal telephone (telephone switchboard, based on ISDN, 4 analogue 
telephones) of my office. 

Can somebody here give me keyword how to search (e.g. with google) to 
realise it?

tia
Ekkard