One GFCI receptacle can serve as protection for several downstream conventional receptacles. An OTG product must have a single micro-AB receptacle and no other USB receptacles. GFCI devices come in many configurations including circuit-breakers, portable devices and receptacles. This standard covers plugs and cord sets that insert into cigarette lighter receptacles. USB cables have plugs, and the corresponding receptacles are on the computers or electronic devices. In such cases, the installer must plug devices directly into building electrical receptacles. Polarized 1-15P plugs will not fit into unpolarized receptacles, which possess only narrow slots. Three-prong plugs do not fit into the older, two-prong receptacles. The 3.0 receptacles are backward-compatible with the corresponding pre-3.0 plugs. The rack consists of a circular array of 40 tubular receptacles. This section is intended to allow fast identification of USB receptacles (sockets) on equipment. Often, 20 ampere circuits are used for general purpose receptacles and lighting. NEMA wall receptacles can be found installed in any orientation. Every day, the MTA removes 40 tons of trash from 3,500 trash receptacles. A building code example is the use of ungrounded ("2-prong") electrical receptacles.