regulation t calls means: Federal Reserve Board Regulation T Margin calls can be issued to customers when they make a purchase. Transaction in a margin bank account that does not comply with the initial minimum Requirement of at least 50 dollars cash, or a loan. The Fed Call is the name for this margin call. By depositing additional funds or making other arrangements, the customer can increase equity. Marginable securities When the required amount of securities or cash is not available. Not deposited in the account during the time specified. Securities may be sold in order to fund the call. The account could also become restricted. (in Stock Market Dictionary)