Hi,
From what I understand in the IB web site is 2:1.

Initial Margin 25% 1 * Stock Value
Maintenance Margin Same as Initial
Reg T End of Day Initial Margin 50% * Stock Value

https://www.interactivebrokers.com.au/en/index.php?f=marginnew&p=stk
https://www.interactivebrokers.com.au/en/index.php?f=marginnew&p=overview3