How to dial 4 digits only out of 8 digit extension

[okeysabbata]

Hi Guys, greetings to everyone.
I am a new member but I have been following your feeds
and they have been very very helpful.

Can someone help me with this,
I have an 8 digit extension number: xxxx yyyy
the digital telephone display the entire 8 digits as the ext
To call another ext on same node I should dial yyyy but to call
an ext on another node I will dial the entire 8 digits.
Both nodes are interconnected by E1

Please can someone help with the way to make this configuration??
Thanks

[vad]

Read system documentation. System doc/ Private network/ ABC-F Homogeneous netw/ ABC-F Homogeneous netw/ Numbering Plan - short local numbering plan.