Prior approval for foreign institutional investments in listed debt securities allows investment subject to Board imposed caps. The amendment exempts investments by a foreign institutional investor, on its own account or for its sub-accounts, in debt securities that are listed or to be listed from the operation of Regulation 15(2) provided the prior approval of the Board is obtained; the Board may, while granting approval, impose necessary conditions including limits on the maximum amount investable by the foreign institutional investor on its own account or through its sub-accounts.