The main distinction is made between outgoing (outbound) and incoming (inbound) routing in telephone systems. Powerful telephone systems often have a variety of criteria which it can use when forwarding telephone calls. For call centres in particular, routing is a key feature of the phone system and essential for the efficient processing of customer calls.
Depending on defined information, incoming calls are assigned to specific individuals, phone lines or groups. Voice response systems are often used to gather information about the caller. They give the caller the option to specify their request in more detail. Using definable criteria the telephone system transfers the caller to a staff member who is suitably skilled to act on the caller's concern. This feature-based routing optimises call agent availability, as well as improving the efficiency of how the calls are handled.
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.