What is the major difference between a sinking fund and purchase fund?

Here is a brief summary:sinking funds use two methods of fulfilling the obligation to retire securities:1. buy securities from interested sellers based on a specific price formula; or,2. call securities from investors, whether investors wanted to give up their securities ornot.purchase funds have only one way of retiring securities:1. buy securities from interested sellers based on a specific price formula.from the above information, you can see that if the sinking fund does not purchaseenough securities from interested sellers, they are then obligated to call back the restof the securities needed. the same is not the case for the purchase fund. a purchase fund attempts to make purchases from interested sellers, but if no one wants to sell orthe price isnt right, the purchase fund will fall short of the intended target.