receiver unit. HTIB systems do not include a television set or monitor with which to display the visual material or a stand to place the receiver unit on. Beside auxiliary inputs, many of them are equipped today with HDMI with ARC, optical and SPDIF inputs. Some HTIB systems are also equipped with a phono input, to allow the connection of a turntable with magnetic cartridge. However such systems are not suitable for vinyl playing as they are mainly focussed on movies and rarely for high fidelity. Some home theaters are just stereo or 2.1, but even so, they are not intended as hi fi, this is just a marketing strategy. There are systems in this class that are sold without a DVD player and are designed to integrate with existing video setups where there is already one, such as a DVD recorder or a DVD/VCR combo unit. The speaker cabinets supplied with most systems in this class are generally fairly small compared to typical stereo speakers, and are meant for wall- or shelf-mounting in tight spaces. There are some systems in this class that are supplied with slim freestanding speakers that stand on the floor. This may be typical of higher-priced systems that are equipped with more powerful amplifiers or most of the "receiver-only" packages that do not come with a DVD player. Some HTIBs use proprietary connectors between components, sometimes even combining several different wires into one connector, to reduce cable clutter and increase the ease of installation. However, this can impede interoperability between different audio/visual devices and makes upgrading certain parts impossible. This may also be used by manufacturers to limit what a consumer can do with a low-end model and encourage them to upgrade should they want more autonomy. A few manufacturers, notably Sony and Panasonic, have implemented wireless connection technology for the surround speakers in this class of equipment. This technology may be available as standard with some of the high-priced models or may be supplied as an aftermarket kit that only works with selected models in the manufacturer's range. It usually uses a line-level feed over a proprietary wireless link to a separate power amplifier used for the surround-sound channels. This link-receiver and power amplifier can be built into one of the surround speakers or housed in a black box that the surround speakers are connected to. Some higher-end HTIB models offer additional features such