Each T-1 has 24 channels (i.e. 24 simultaneous conversations) - unless you run it through a concentrator, in which case you can get up to 96 conversations out of each one - but at a price.

Assuming standard service, depending on your traffic you would probably need 3 to 4 T-1s. We used to figure 100 DIDs on 12 - 16 trunks. At that level you would need 1.5-2 T's just for incoming, leaving 1.5 -2 T's for outgoing. Assuming no compression, you could have 36-48 simultaneous outgoing calls and 36-48 simultaneous incoming calls.

Depending on your carrier and your PBX you may be able to get "dynamic" T's that are not fixed to X number of Incoming and Y number of outgoing channels, but instead dynamically reconfigure depending on your traffic. Failing that you may be able to split some of the T's (i.e. half incoming DIDs and half outgoing DODs) this will give you a little more protection in the event of a failure.

Determining traffic is a whole science (maybe really an art). I used to do quite a bit of it, but that was 20 years ago and I'm more then a little rusty. You should run traffic studies on your current configuration (most PBXs & COs support this) and then determine your needs from there.


Sam

"Where are we going and why are we in this hand basket?"