the color black. blanking interval Period during the television picture formation when the picture is suppressed to allow the electron gun to return from right to left after a line (horizontal blanking) or from top to bottom after each field (vertical blanking). blanking pulses The process of transmitting pulses that extinguish or blank the reproducing spot during the horizontal and vertical retrace intervals. block In H.261, a block consists of 8 pixels by 8 pixels. It is the lowest element in the hierarchical video multiplex structure, which, at the top of the hierarchy, includes the picture, then a group of blocks, then a Glossary of Terms macroblock and individual blocks that comprise the macroblock. A block can be of two types, luminance or color difference. One of three additive primaries and B in the RGB. Refers to Bayonet Neill-Concelman. A twist-lock connector widely used for the connection of video cables. board Boards consist of a flat backing made of insulating material and inscribed with conductive circuits etched on their surface. A fully-prepared circuit board is meant to be permanently affixed into a system as opposed to a module that is meant to slide in although the terms are now used interchangeably. See Bell Operating Company. Also referred to as Regional Bell Operating Company or RBOC. BOnDInG Bandwidth On Demand Interoperability Group. This consortium of over 30 vendors developed the standard for inverse multiplexing that carries their name. Version 1.0 of the standard, approved in August 1992, describes four modes of inverse multiplexer interoperability. It allows inverse multiplexers from different manufacturers to subdivide a wideband signal into multiple 56- or 64 Kbps channels, pass these individual channels over a switched digital network and recombine them into a single high-speed signal at the receiving end. The speed at which bits are transmitted over a communications medium; in other words, the number of bits that pass a given point in a communications line in one second. The term 