This excerpt taken from the PPL 10-K filed Mar 1, 2005.
8. PROCEEDINGS, ACTION AND INDEMNIFICATION
(A) THE Trustee shall not be bound to take any proceedings mentioned in Clause 7(A) or any other action in relation to these presents unless respectively directed or requested to do so (i) by an Extraordinary Resolution or (ii) in writing by the holders of at least one-quarter in principal amount of the Securities then outstanding and in either case then only if it shall be indemnified to its satisfaction against all Liabilities to which it may thereby render itself liable or which it may incur by so doing.
(B) Only the Trustee may enforce the provisions of these presents. No Holder or Couponholder shall be entitled to proceed directly against the Issuer to enforce the performance of any of the provisions of these presents unless the Trustee having become bound as aforesaid to take proceedings fails to do so within a reasonable period and such failure is continuing.