rical signals to RF signals. The point from which broadcasts originate is the hub. The hub has a large dish, routing equipment, and fiber links to the enterprise's headquarters for commercial customers. All communications broadcast from the hub travel up to the satellite and then down to the ground stations (the satel- lite dishes). Satellites are used to broadcast television and radio signals and to transmit posi- tioning information to aircraft and air traffic controllers. Satellites are particularly suited to broadcast signals to large areas for applications such as weather monitoring, mapping, and military surveillance. Satellite Telephones The phones associated with these services are larger, heavier, and more expensive than cellular phones, and per-minute rates are high. However, during catastrophic disasters, they are sometimes the only operational service because of damaged or destroyed cell towers and lack of electricity at cell sites. They are often used in war zones where com- mercial facilities have been destroyed. They are also used on tankers, fishing vessels, and geology expeditions, and in remote mountainous regions where cellular service is not available. Because geosynchronous satellites are located SO high in orbit, there is an inherent delay of a half second or SO in voice and data transmissions. This delay is the result of the time it takes the signal to travel to the satellite, be processed by the satellite, and then travel to the receiving station. Thanks to improvements in technology, today this delay is barely perceptible. In the 1970s and 1980s, users who placed calls to interna- tional locations often experienced delays of several seconds, which could make it quite difficult to carry on a conversation. If both parties in a telephone call spoke at the same time, parts of words were "clipped." New, High-Frequency Satellite Service for Airplanes and Internet Access Satellite service is now used to transmit TV, movie, and data signals to Wi-Fi access points on airplanes. These newer satelli