One example of how outbound routing can be used in telephone systems is when finding the most favourably priced telephone provider for specific calls. The technical term for this is Least Cost Routing. The method generally uses the Call-by-Call feature, automatically comparing pricing tables. By using a call prefix number that is automatically pre-selected by the system, every call can be routed via the call provider that is offering the cheapest rate for that specific call. Call-by-call, however, must be supported and enabled by the user's own telephone provider. The Least Cost Routing function can be implemented through software in a telephone system or additional hardware.