Outofarea

Outofarea is a phenomenon that occurs in telephone systems, particularly in public switched telephone networks (PSTN). It refers to a situation where a caller is unable to reach a particular phone number or area code because it is deemed to be out of area. This can happen for a variety of reasons, including exchange capacity issues, long distance routing problems, or even temporary service disruptions.

In the past, outofarea was a common issue for long distance callers, particularly those using rotary phones. When a caller would dial a number that was out of area, the phone would begin to signal with a fast series of buzzer tones, hence the term "out of area". This issued would often be resolved by simply dialing the operator and asking them to complete the call over a long distance trunk line.

However, with the advent of digital phone systems and the widespread use of cell phones, outofarea has become less of an issue. Modern telephone systems can often route calls around capacity bottlenecks and long distance routing issues, reducing the incidence of outofarea. Nonetheless, it can still occur in certain situations, such as during high pressure call volumes or when there are widespread service disruptions.

From a technical perspective, outofarea is often related to the concept of least cost routing and near-end/ far-end congestion control. This involves the selective blocking of incoming calls based on factors such as overload conditions, unavailable direct call completion, and trunk overload. This selective blocking is designed to prevent overload of the network and ensure that calls can be completed as efficiently as possible.

Despite being relatively rare in modern telephone systems, outofarea remains a topic of interest among telecommunications engineers and historians of telecommunications technology.