What are the different types of Margin Calls?

Maintenance Call – when account equity is below the minimum maintenance requirements for open positions.
Reg T (Initial) – when there is Insufficient Overnight Buying Power to satisfy initial requirement on opening transactions held overnight. Reg T states you can only borrow up to 50% of the total purchase price of stock on initial opening transactions.
Equity Maintenance Call - Patterned Day Trading account falls below $25K minimum requirement.
Day Trade Call - is when customers opening transactions exceed the customers DTBP and then positions are closed on same day.