*PBX Hardware Questions

Hi, I’m an IT guy that got thrown into the world of IP telephony when my managers asked me to convert our standard PSTN/PBX office system to a full VOIP/IP-PBX system. We hopefully want to cut monthly telcom costs and improve functionality over our 10+ year old PBXs.

Telephony: We currently have a T1 that terminates at an Adtran 624 that splits into 20 analog lines that run to one of two PBXs. I know the T1 does not carry an ISDN PRI currently.

Internet:Business class cable modem to a cisco router/firewall to switches


  1. is it feasable to build an * system that uses the T1 (connected via a Digium TE121 card) for external inbound/outbound. The T1 would be split between a VOIP ITSP for all calls & a local telco for fax/911/alarm service. Digium’s info on the card says it can split a T1 to 12 digital and 12 analog channels. Internal inbound/outbound would use a 1AEX440EF for the fax and alarm lines and the computer’s ethernet connected to a switch for the VOIP phone system.

2)If the above setup would work, that would mean we could get ride of the adtran. Is there anything about the T1 line that would need changing or verified before this was done, other than getting pricing for data channels instead of analog?

  1. I talked to a sales rep for the T1 company that also provides our telephone service (It leases lines from Verizon) and he said that I could not do VOIP using our current T1 line, even if I found a VOIP provider to act as an IP to PSTN trunk(right terminology?). Is that B.S. to keep us from switching providers?

  2. Are 800 numbers able to be transferred from a PSTN telco to a VOIP provider?


I think that should work, as long as you are expecting 12 ports for digital audio through your current provider, and approximately 770k for internet/SIP traffic to your new ITSP. If you are expecting to use only SIP traffic, you’d just get a data only T1 and have the 1.54Mb for internet/SIP.

Depends on what you want to do, see above question :smile:

He is probably right in that you couldn’t do VOIP with your current T1 if it is voice only and no data. Ask him about converting your current T1 to a data T1 and if they can then provide SIP services for you. I believe Verizon does have a SIP trunking product.
Here is a link to their wholesale portal www22.verizon.com/wholesale/solu … rvice.html



Thanks a lot dave. Still so much to learn!