Zyxel G-4100v2 | console settings

Hello,

We are having more that 200 zyxel routers in our company.
G-4100v2. I would like to connect to this device via console and made some modificaations, because original software is with bugs.
I am thinking about putting Pyramid Linux inside for testing.

Do you have someone experience with this?

1. which cable should we use, it is a standart NULL-modem cable, with statndart pinout?
2. If not which cabel should we use?
3. What is the console port settings (baud rate and so one)?

I've tried several combinations, but none workded.
Please advice, our problems with Zyxels started to be critical.

Thanks,
FL