A port count is a number used by manufactures as a Sale point; "System ABC with 96 Ports" as an example.
The Sale Point: 96 ports available, but the actual configuration of the system determines the number of Trunk Ports, Digital 'Set/stations' ports, and Analog Ports.
Thus an 18/32 Executone system has a Sale point of 50 ports (where 18 are reserved for Trunks/CO's and 32 are reserved for sets/stations)..
The Nortel Meridian 1 Option 81C has a sale point of 10,000 ports, but that doesn’t mean you’ll get 10,000 sets/stations – it actually means that you have a combination of Trunks, Sets/Stations, etc. equal to 10,000 ports total. (Sets and Stations are used interchangeably and refer to Digital or Analog ports.)
And in some systems SDI ports actually subtract from the total ports available.
The Configuration (Legacy Systems): Ports are set by the card installed - As an example; A digital Line Card for a Meridian 1 takes up 16 ports (even if you only use 2 ports – the remaining 14 ports are now reserved for digital sets and can’t be used for anything else and is subtracted from the total ‘sale’ ports of the system).
With a legacy system (those systems that use Central Office (CO) trunks to communicate the PSTN (Public Switch Telephone Network), Trunk Cards and Station Cards are usually set to a suggested ratio of 20/80 (20 percent for trunking and 80 percent for stations) – This of course is dependent of the use of the system. I work at a 1,800 room resort and our ratio is actually 25/75 - this ratio shift accounts for the number of concurrent conversations among the 1,800 guest.
The Here and Now: It’s actually better now-a-days (with the invent and propagation of Voice over Internet Protocol) to refer to stations/sets as endpoints and interconnected systems as nodes. So if you see a mention of endpoints – that’s referring to stations.
Hope that kind of explains it…
You might want to check out my PSTN Flash file on the Nortel Portal;
http://nortel.pbxinfo.com/index.php?...play&ceid= 11 Chas2002