Is it permissible to purchase electrical appliances by installments, with the price being determined at the time of receipt after seven months?

If the inquirer purchases described, unparticularized devices to be received after seven months, this is a Salam (forward) sale, and the full price must be paid upon contract, with no deferral or installment allowed. However, if he purchases specific, identified devices and leaves them with the seller to be received later, there is no objection to paying the price in installments. In both cases, the price must be determined at the time of the contract.