A keypunch or key punch is a device used for precisely punching holes in specific locations on a stiff card. It was used in conjunction with early punched card computers. The punched card served as the program instruction for the computer. The locations of the punches were determined by the keys being struck by a human operator, much like typing...
An extended service set (ESS) is one or more interconnected basic service sets (BSSs) and their associated LANs. Each BSS consists of a single access point (AP) together with all wireless client devices (stations, also called STAs) creating a local or enterprise 802.11 wireless LAN (WLAN). To the logical link control layer (part of layer 2 of the 7-layer OSI Reference Model) the ESS appears as a solitary BSS at any one of the STAs.
The most basic BSS consists of one AP and one STA. An extended service set, consisting of a set of BSSs, must have a common service set identifier (SSID). The BSSs can all work on the same or different channels. This helps to boost the signal throughout the wireless network. A single service set consists of all STAs receiving signals from a given AP and creates an 802.11 wireless LAN (WLAN). Each STA may receive a signal from several APs within their range. Depending on its configuration each STA can, manually or automatically, select the network with which to associate. And multiple APs may share the same SSID as part of an extended service set. Although not part of the 802.11 standard, some wireless APs may broadcast multiple SSIDs, allowing virtual access points to be created – each with their own security and network settings.
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