Originally Bell Telephone Laboratories, the research arm of the Bell System. When AT&T divested itself of its regional telephone companies, Bell Labs was split. One division, still called Bell Labs, belongs to AT&T and is a proponent of a particular ATV system (SLSC). The other division, called Bellcore for short, belongs to the Bell regional holding companies (RHCs) and is, among many other R&D projects, investigating mechanisms for reducing the bit rate of digital video transmission, which may be applicable to ATV. Bellcore has formed a joint venture with NHK for HDTV research.