They are coin operated machines which are used in selling several products such as milk, soft drinks, chocolates, platform tickets etc in many countries. The latest area in which this concept is getting popular is the case of Automated Teller Machines (ATM) in the banking service. They made it possible to withdraw money at any time without visiting any branch of a bank. They can be useful for selling pre-packed brands of low priced product which have high turnover and which are uniform in size and weight. However, the installation cost and expenditure on regular maintenance and repair of these machines are quite high. Moreover, the consumers can neither see the product before buying nor can return the unwanted goods.