[Asterisk-Users] Newbie: ISDN and Capacity Planning

[Chris Travers]

Hi;

I am in the process of planning a PBX/Voice mail system for a business 
with an ISDN phone system and somewhere on the order of 12 internal 
phones.  The ISDN system appears to be a Primary Rate Interface, though 
this may be irrelevent because receptionists answer all inbound 
telephone calls before possibly transferring via the PBX, and most calls 
do not get transferred.  Telephone use might be considered to be average 
to low among those with internal phones (most contact is done via face 
to face though occasional calls must be placed out).

Any advice on capacity planning?  How many lines should one plan on 
having available via the PBX in general?  Any advice on calculating this?

Additionally, the PBX is replacing an old system (80286-based) due to 
the fear that a failure of an ancient piece of hardware could take down 
their phone system.  Are there any hidden gotcha's that people think I 
should be aware of?

Best Wishes,
Chris Travers
Metatron Technology Consulting