And some more info on your PBXs would still come in handy:
Depending on the interfaces provided by your PBXs to talk to anything else you will need the appropriate interfaces on the Asterisk boxes.
I.e. if your PBX provides a PRI (T1 or E1) interface, you’ll need a corresponding interface on the Asterisk; if it provides BRI ISDN interfaces, you’ll need a BRI ISDN interface on the Asterisk box. If you want to use a normal (analog POTS) FXO interface on the PBX, you need a FXS interface on the Asterisk; if you want to use an analog (POTS) extension interface on the PBX, you’ll need an FXO on the Asterisk.
Now, since you didn’t seem to realize that this information is absolutely essential to anyone wanting to answer your original question, it was not so inappropriate to give you an RTFM answer – you might have found that out from reading the recommended sites.
And these sites will also tell you what is available for Asterisk for each of the above mentioned interface types, so I will repeat WillKemp’s recommendation that you go read especialy voip-info.org/wiki/view/Asterisk and the hardware sections there.