What is the 50:50 rule with respect to margin deposit?

As per regulatory directives, the margin benefit available against non-cash securities cannot exceed the total margin benefit available against cash and cash equivalents.Let�s understand through an example:A.Total cash and cash equivalents?100Total haircut value of non-cash securities?80Total margin available to the client for trading purposes?180 (?100+80)(In this case, the client is eligible to receive the full margin benefit of non-cash securities as a higher margin benefit against cash and cash equivalents is available to him)B.Total cash and cash equivalents?100Total haircut value of non-cash securities?150Total margin available to the client for trading purposes?200 (?100+100)(In this case, the client shall be eligible to receive a margin benefit of only ?100 against non-cash securities as the margin benefit available to him against cash and cash equivalents is ?100 only)C.Total cash and cash equivalents?0Total haircut value of non-cash securities?200Total margin available to the client for trading purposes?0�(In this case, the client shall not be eligible to receive any margin benefit against non-cash securities as the margin benefit available to him against cash and cash equivalents is nil)