Using excess equity as buying funds?

I've been playing around with Zorro for a few months now, and there is one thing that still surprises me to this day:


A margin call only happens when Equity curve meets Margin, but not when Margin meets Balance.

My question is:

Is this a normal practice allowed by the brokers?
Let's say, could I try to buy on equity instead of balance with e.g. IB and not get a margin call?

I'm not aware of this practice, but suppose that some stock brokers allow it, f.i. IB. If you do that, you must calculate your capital requirement based on MAE, not DD. Where is the quote from?

Thank you for your answer jcl!
Sorry, thats not actually a quote, I just put the core sentence of my question into a box for better visibility. It is just a fact about Zorro that I observed experimentally.

EDIT:

Indeed, IB calls this concept "Equity with Loan". Am I the only one who thinks that this is a gold mine? Never sell any decent asset ever again! Just buy new ones on Equity won!
Here is a picture from their website: