*local area networks usually use cabling for connecting devices. However, there is another alternative: wireless or infrared transmission. Each device on a network which uses this form of communication is connected to its own transmitter and receiver and communicates using the same protocols that are used in cable access. Such networks are employed when users move around a building or where the building might be unsuitable for cable transmission, such as an old building with strict regulations about what modifications can be made to its fabric. Such wireless networks are expensive, have poor security, and are easily affected by electrical interference. As well as these local area uses for wireless technology there are a number of technologies that allow the mobile user to connect into networks, including Circuit Switched Cellular, Cellular Digital Packet Data, and private packet radio.