KLkey stream A stream of characters used as a security key in various data encryption algorithms L2TP Layer 2 Tunneling Protocol. A protocol used for securely connecting VPNs over unsecure transmission media such as the Internet. LAN local-area network. A local group of computers and other network devices connected together in one area. Layer 2 roaming Roaming between or changing connections from one AP to another where the APs are connected to the same IP subnet. Layer 3 roaming Roaming between or changing connections from one AP to another where the APs are connected to different IP subnets. LEAP The Cisco proprietary Extensible Authentication Protocol. lightning arrestor A protective device that provides a very low-resistance path to any voltage above its rated value. It is designed to protect against nearby lightning strikes or static, sending the energy to the ground to prevent damage to equipment. linear amplifier A device that accurately reproduces a radio wave in magnified form. link budget A mathematical model of a wireless communications link that accounts for a wide variety of factors that affect operating range and performance. Sometimes called a path budget. LNA low-noise amplifier. Typically a small-signal amplifier for RF receiver applications. local-area network See LAN. LoS line of sight. An unobstructed straight line between two transmitting devices. Line of sight is typically required for long-range directional radio transmission. Because of the curvature of the earth, the line of sight for devices not mounted on towers is limited to 16 miles (26 km). low-pass filter A signal filter that passes all frequencies below a certain frequency and attenuates all higher frequencies.
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