h 480 channels. It is equivalent to 16 E1 circuits. DS-3 (Digital Signal level 3) E-911 (Enhanced 911) The T3 transmission rate of 44Mbps over 672 The capability for agents who answer 911 associated channels. (T3 is equivalent to 28 calls to receive the callers' phone numbers T1s.) and locations. DSP (Digital Signal Processor) EDGE (Enhanced Data Rates for Compresses (shrink the number of bits Global Evolution) required for) voice and video, performs digi- EDGE mobile services offered by cellular tal-to-analog and analog-to-digital voice con- carriers have higher data rates than second- versions, and packetizes voice and video in generation cellular networks. EDGE is often used by carriers as they transition to higher- real time for IP networks. data-rate, third-generation mobile service. DTE (Data Terminal Equipment) end offices Devices that communicate over telephone The central offices connected to end users and lines. Examples include multiplexers, PBXs, to tandem central offices. Most end offices key systems, and personal computers. are based on circuit switching, but they are slowly being converted to softswitch technol- DVB (Digital Video Broadcasting) ogy to carry VoIP. A standard approved by the European Tele- communications Standards Institute (ETSI). endpoint Any device connected to LANs, such as com- It has lower resolution than HDTV. puters, printers, and VoIP telephones. DWDM (Dense Wavelength-Division Ethernet Multiplexing) Based on the 802.3 standard approved by A way of increasing the capacity of fiber- the IEEE. It defines how data is transmitted optic networks. DWDM carries multiple on and retrieved from LANs. It is used by colors of light, or multiple wavelengths, on devices such as personal computers to access a single strand of fiber. Also known as Wave- the LAN and to retrieve packets carried on the LAN. length-Division Multiplexing (WDM). Exabyte (EB) A unit of measurement to indicate the num- The European standard for T1. E1 has a speed ber of bytes in storage networks. An Exabyte of 2.04