Asterisk and analog PBX

i’m a total newbie with voice over ip, and a little bit confused to understand when using an analog PBX with Asterisk
in an IP Voice environment, what can be the use of an analog PBX? an ATA?
in other terms, if we have an analog PBX, how can we integrate it with asterisk? Thanks!

Is this a PABX or a PMBX? (I guess PABX.)

If PABX, does it support MF4, or is it loop disconnect only?

Is Asterisk down stream or upstream relative to the PSTN? Or is it in a tie line relationship?

If in a tie line relationship, what trunk signalling is used?

Why do you think you need to add Asterisk to this system?

Basically, you need to do more background reading. The brand and model might also help.

If Asterisk is down stream of the PABX, you will need an FXO card or an FXO gateway, the latter is similar to an ATA, but detects ring current rather than generating it. If you only have loop disconnect signalling, you may have no choice but to use an FXO card.