German industry association whose name translates loosely as “German committee for terms and conditions of sale”, nowadays known as “Deutsches Institut für Gütesicherung u. Kennzeichnung e. V.” but still uses RAL as a trademark. Originally founded in 1925 as a self-regulatory umbrella body whereby companies and traders in specific business sectors could band together to form quality standard committees, each of those is intended to publish either a requirement for membership of a specific committee, specific quality standards or rules of trade, or both. Fulfilling these then allowed you to display the RAL logo and sub-committee name on your product as a quality mark.
Note that the Reich in the name refers to Germany and not the state of Germany, i. e. this is not an official state sanctioned, run or owned organisation and has never been. There is a tendency to form those committees only in cases where there is a perception in the market of unfair competition practices such as mis-selling and labelling of products or unfair trading terms, thus fairly fast moving markets like consumer electronics have often seen RAL committees come and go and on the other hand very conservative markets like traditional musical instrument building have not seen a need for such marks since the quality and business practices were already well established in the sector even though they had not been standardised.
But RAL marks show up on electronic consumer equipment and musical instruments from time to time but it is important in those cases to note what the sub-committee is since the standards enforced could be technical, rules of trade or even business ethics. Best known for on one hand gemstone guidelines and on the other the colour code specifications used in the paint industry but the RAL colour code is the only universally accepted colour code system even though ISO and others have proposed alternatives. Homepage:http://www.ral.de
R&D = Research and Development Actually meant to describe the work involved in preparing for future products and/or services, but it's usage is mostly to identify the divisions that perform said work or even the buildings that house them.
RF = Radio Frequencies Basically all electromagnetic waves that are shorter than infrared light. Usage is changing slightly, traditionally this was just the parts of the spectrum that you associated with radio communications (i.e. nothing above microwaves) but lately there is a tendency to include the whole shebang including some light waves and even in some cases other radiation etc..
Rochelle Salts = Sodium Potassium Tartrate Crystal structure that is used in low budget transducers such as microphones and pickups, a very efficient as a transducer and cheap to make but it dries up with age and thus needs replacing every now and then and has for the most part been replaced with ceramic elements which show a similar behaviour but are more robust and have a greatly extended lifetime.
RoHS = Restriction of Hazardous Substances A directive put out by the European Union that restrict or bans the usage of certain hazardous material inside the EU to minimise the contamination of landfills and to protect the health of industrial workers. While the directive touches on a large number of substances the ones that apply to the electronics industry are mostly in regards to the use of lead, halide and mercury in the manufacture of PCB's and in soldering of electronics onto such, cadmium as is used in batteries etc., hexavalent chromium and other heavy metals used in sundry electronic and media manufacturing.
In most cases RoHS directive places an absolute ban on any product or process containing any of the materials listed, regardless of if it is for consumer or professional usage. This means in practice that you can for instance as an individual import a vintage amplifier that you already own but cannot import a new or vintage amplifier that you buy from outside the EU unless a RoHS certificate for it is on record, you can build a new amplifier using materials such as lead soldier that are not compliant or repair one yourself, but cannot sell or service an amplifier using such for a fee even in single quantities.
Most Asian manufacturers have converted their product lines wholesale for RoHS compliance but a number of North American manufacturers run specific product runs for the European market, so if you are purchasing a hi-fi product directly from a non EU manufacturer via mail order ask for a RoHS compatible version. See this page from the UK gov. for more compliance information.
RPM = Rounds per minute The number of revolutions a disk based media does each minute, in analogue media in particular the speed of the revolution is a trade-off between quality and playback time, with all other factors being equal a higher playback speed means better sound quality (more information read off the disk) but in turn means that there is less time available on the media for program material. This term is only used for media that rotates at a constant speed.
RRP = Recommended Retail Price A guideline price for a product given out by the manufacturer or distributor as to define a maximum price to be paid for the unit. This is not actually done for the benefit of the customer but for the benefit of the manufacturer since it allows him to set a certain price point for public relations purposes. The definition of this used to be fairly fixed some 30 years ago when retailers got a more or less fixed 40% off an RRP as their purchase price and that meant that price variations were small from retailer to retailer, but changes in business practises have meant that the term has become increasingly loose and some manufacturers use it only as a vague indicator.
RS-232/RS-422 A standard for serial digital communications that is so widespread in the computer and CE industries that the word serial is used as a synonym for it. RS-232 was initially put forward in 1961 as a standard interface for modem control and therefore has terminology which assumes a control unit and a slave but modern variants are fully bi-directional as far as control is concerned. The standard is too slow to carry audio data with modern variants of it not exceeding 115k bits in most cases but this is more than enough to carry control information and program data and it's exactly in those situations where you will find it used.
Since even the cheapest low power microcontrollers have a serial port interface built in which means that implementing it is free or at the least only at costly as the connector used from the designers point of view, you will find that audio devices such as DAT recorders, AV amplifiers and even something as cheap and simple as low cost universal remote controls have external, internal or hidden RS-232 interfaces that can be accessed by technicians for analysis or upgrades, or by end users for remote control, synchronisation or other utilitarian purposes. There was for instance for a time a serial interface on every Sony product that featured a recording button except for the cheapest systems.
The latest published standard is RS-232D xxx which incorporates improvements found in CCIT V24 (USA) and in ISO IS2110 (Europe) but there may have been updates to those standards since the last time I fell asleep reading technical manuals. RS-422 is an improvement of the 232 standard that features balanced connections and has data transfer rates of up to 10M bits, now that is enough to carry audio data and you will find variations of this standard used in professional digital audio recorders, most Sony professional digital recorders had this at the least as an option and even DSD interfaces from the company (for recording SACD material) sport such an interface. Other variations on this standard exist including RS-423 (Unbalanced 422 variant) and RS-449 (High speed 232 variant) but are seldom used outside the computer communications industry.