[Asterisk-Users] caller id?

[Altus Syman]

Good day all
I'm new with asterisk.I have a question about it.
If I have a gateway box with a zaptel cad and sip users using sip 
phones!If someone call from the outside and dial the extension of the 
sip user,will the number from the outside show on his phone?
In other words,can/how do I get caller ID from outside(pstn) coming in 
to the gateway(zaptel card) to the sip users?
Does this make sense
I want the sip users to se who is calling from the outside?
Please help and advice
Altus