nd quality. They can also quickly set up portable cell sites and additional generators at towers or mobile switches that lose power. This enables mobile providers to restore service to these areas. In addition, if one part of the country is hit by a natural disaster, other carriers will send staff members and equip- ment to assist in restoring service. Carriers plan for emergencies in various ways. For example, they build backup wireless routes between critical switches and public safety answering points (PSAPs) for E-911 calls. They also look at ways to increase security against hackers and terror- ists at peering sites where carriers exchange IP traffic. In addition, providers consider methods to avoid user errors. User errors occur most often during network upgrades and programming changes. Electrical Requirements for Towers, Residential Service, Digital Loop Carriers, and Digital Subscriber Line Access Multiplexers Prior to the use of Digital Loop Carriers (DLCs) and Passive Optical Network (PON) equipment, telephone companies supplied low-voltage, direct-current electrical power for residential telephones on the copper cabling that carried telephone signals. The power was carried from the central office to customers and each central office was equipped with generators and backup batteries. Thus, during disasters when commer- cial power was lost, telephones still functioned. However, equipment connected to fiber at customer premises and DLCs requires electricity to operate. In addition, equipment at cell phone towers requires electricity to operate. This is a problem because there are many more of these devices than there are central office switches, mobile switches, and IP voice servers in the network. Thus, it is more complex and costly to provide backup power in the form of long-lasting bat- teries or generators for all of these devices to keep them operational in power outages. During these times, it is common for all of the switches to be operational; however, Signaling the gear located between the custo