The Defense Switched Network is a telephone system that's been around the military for more than 100 years. In recent years, some users have forgotten this network when making a long-distance telephone call.DSN is designed to support the Department of Defense and U.S. government to allow users to call from post to post or other military branches within DOD, explained Chuck Shellman, a Fort Knox telecommunication specialist."It's a group of government owned and leased physical cables that interconnect everything and we can use it free of charge worldwide," he said.Shellman said DSN is still available to DOD because individuals are supposed to use the network when making a long-distance telephone call."If there is a DSN connection where you are calling, you should always use DSN first because it's free," said Shellman. "You are not going to get in trouble (if you don't use DSN), but you are spending money needlessly. If one or two people are doing it, or even 50, it's not going to be a big thing. But, with 19,000 or 20,000 phone users on this post it could become an issue really quick."In prior years the government would make sure there were DSN connections available in all buildings but that has changed in recent years."With technology advancing, we've gotten discount rates on commercial numbers and the government leasing facilities in the commercial world," he said. "It's not cost effective to put in a DSN connection. We have commercial leases which give us a huge discount on calling long distance."Mark Bunch, the Fort Knox Network Infrastructure Division chief, said that individuals in the government at the organization and tenant user level deal more and more with a public that isn't government related and doesn't have DSN capabilities."We are finding ourselves using long distance more and more just in our day-to-day work to communicate with agencies we need to do business with," Bunch said.Shellman said individuals should still use the network because doing so saves the government money.What is DSN?The Defense Switched Network is the principle long haul voice communications command network with the Defense Communicating System, providing nonsecure direct-distance dialing service worldwide through a system of government-owned and-leased automatic switching facilities. The purpose of DSN is to handle essential command and control, operations, intelligence, logistical, diplomatic and administrative traffic.How to use DSN-Verify the DSN number desired. -Listen for dial tone. -Dial the DSN access code 94. -Listen for the second dial tone. -Dial the seven-digit DSN number.