As the industry matured, more complex features were added to vending machines. First, sound and audio recordings were added to promote the use of machines. A machine might thank customers for their purchases, or recite a slogan for the product being vended.
A second added feature which became increasingly important (as taxes on vending machine items came into the picture) was a vending machine’s ability to make correct change for a customer. Primitive methods included taping pennies to the package inside the machine or placing pennies in the individual slots of each item so that it would be dropped out for the customer upon their purchase. This method only worked if a customer paid a certain amount for the item, and didn’t work if they had exact change. Also, it required a lot of manual labor to fill the machines properly.
Another feature that increased a machine’s efficiency was increasing the capacity of the machine. By increasing the amount of product that a machine could hold, it would decrease the amount of occasions necessary for a serviceman to stock a machine.
Standardized packages were key to the success of the vending business as well. Advertising could dictate what each product would consist of, so that vending machines could simply carry the brand name on them. For example, today when a customer purchases a bottled Coca-Cola from a vending machine, they know exactly what product and how much (unless otherwise specified on the machine) they will be receiving. This familiarity with products helped customers feel more comfortable with buying products they could not see before the purchase was made.
Refrigeration and heating systems for machines were not developed until the late 1950s. When this feature became a reliable option, more products could be sold. The method prior to electric cooling required large blocks of ice to be stocked daily in order for drinks to be cooler than the ambient temperature. This was largely ineffective because the ice melted before the end of the day, leaving luke warm beverages or spoiled milk.
Another profitable factor of vending machines is the use of vending machines allowed stores to vend their merchandise after hours. While department stores themselves still had hours of operation, vending machines placed outside of the store could provide essentials at any hour. As more products became available this feature became more important. For example, convenience stores would stock toiletry items and cigarettes in machines so that these items could be purchased day or night.
Finally, anti-slug technology became more effective, using complex processes that measured, weighed, bounced, and checked coins for magnetization. The 1930s saw a turn in production for more effective machines that, in turn, were more profitable.
While many other advancements and special features are now available, these were the first handful that really revolutionized the industry. Please see the Impact section for further advancements in vending machine technology.
 Kerry Segrave, Vending Machines: An American Social History, (Jefferson, NC: McFarland & Company, 200), 27.
 Ibid., 27-28.
 Ibid., 28.
 Ibid., 30.
 Colin Emmins, Automatic Vending Machines, (Cromwell House, UK: Shire Publications Ltd., 1995), 16-18.
 Segrave, 15.
 Ibid., 31.
 Ibid., 116-118.
 Roger Smith, editor, Inventions and Inventors, (Pasadena, CA: Salem Press: 2002), 851.