If the client have a T1 in his OLD pbx (PABX) and he wants to have one asterisk for testing… How can i interconnect BOTH PBX if is just one cable (T1 cable)?
Put Asterisk in front of the old PBX then, e.g.:
PSTN -> 1st T1 port in Asterisk > Asterisk processing > 2nd T1 port in Asterisk > only T1 port on existing PBX.
So, i will need 2 T1 ports in the asterisk for this right?
Yes. If your existing PBX only has one T1 and you want Asterisk to be in the mix, then Asterisk will have to be in front of the PBX. One side of Asterisk faces the PSTN, one side faces the PBX. Each “side” then is a T1, so you need a two port T1 card. I recommend Digium cards. 
Ok, Digium, but the card without the Echo Cancellation Module works well with OSLEC?
No idea, OSLEC isn’t something we’ve written, nor is it something we test. The safest thing you can do is just buy one of the two port cards with the hardware echo cancellation module. Really. It’s more out of pocket money, but it’s less trouble / support / debugging / headaches / etc. on the backend. And, if you get into the project with OSLEC and find it doesn’t work, then you’ll have spent a lot of time / energy to figure that out, and you’ll end up buying the hardware echo cancellation module anyway. It’s easier to simply buy it up front, and never have to worry about it.
Good Point! Look malcom i have wrote somes post days months ago about the delay with Fxo ports and hangups, i have interconected an NORTEL PBX with asterisk using an ATA device, and when the norstar call to asterisk, play the IVR and hangup the handset, the asterisk keep executing the dial plan and somes 10 or 11 seconds after, hangup the line.
Everyone says about line supervision, but… in this case i wasn’t using the PSTN, i was using direct Line from nortel norstar to asterisk
Uisng a TDM400P not PRI. because PRI have pritimers=> but with analog cards, we don’t have parameters to manage
The TDM400 went end of life quite some time ago:
digium.com/en/products/eol.php
so we no longer provide support or assistance when using it; nor do we make any driver changes.
Question: All T1/E1/J1 cards are PRI?
Yes, all of the T1/E1 digital cards that we build support PRI signaling.