DOBM = Digital Output Bi-phase Mark Code
A binary data stream where the clocking signal modulates the binary signal using frequency shift keying to get a binary stream called "Bi-phase Mark Code" which can then be used to decode a correct clocking frequency from the binary stream and do away with the need to send a separate clocking signal. The other advantage of using FSK is that using a normal digital signal involves using a voltage swing to differentiate between the 1 and the 0 and this can cause interference in the analogue stages of audio equipment and using longer leads will have a deteriorating effect on the signal, in a BMC the 0 and the 1 have the same amplitude but different polarities and this makes it more suitable as a distribution since signals can be sent using very low power and still survive intact at the receiving end (S/PDIF uses 0.5 to 0.6v peak to peak for instance).

DOBM is for all intents and purposes S/PDIF, it is in other words the binary stream read off a CD alongside housekeeping data modulated with the players clock (headers are kept unmodulated for synch purposes), and most Compact Disc DSP/control chips have a DOBM output on them alongside an I2S output so if you have a CD player that lacks an output you can actually hook a connector to the DOBM pins and connect that to a DAC, although technically you are suppoed to process the signal a bit, a transformer will do. There are problems with this technique in audio usage, Jitter is always introduced for instance.

DO NOT FIDDLE WITH
An independent tape guide with a pressure mechanism that kept a large loop of tape tight. Used in electronic music creation to allow people to have huge tape loops or to use multiple open reel tape recorders to do audio loops with, either for rerecording onto a loop a la musique concrète or for multi-tap delays, if you had multiple DO NOT FIDDLE WITH's you could also run the tape recorders at different speeds, highly useful for multi-tapped delays.

Since these were never sold commercially they were invariably home made using some ingenious and some not so ingenious methods to stretch the tape without breaking it, the BBC used a microphone stand with a spring attached to it, fastening them to walls with elastic rubber bands was also popular, but both of these solutions would not take enough slack for huge loops or handle recorders with quite large differences in speeds so someone came up with the ingenious idea of fastening tape guides to helium balloons ... which works like a charm and provides a nice visual effect to boot for live shows.

The name comes from the BBC Radiophonic Workshop, but someone had written "DO NOT FIDDLE WITH" on one of the modified microphone stands and the name stuck.

Of course a much better solution to this problem was to be found in the tape loop box where excess tape in a loop folded itself, as used in many commercial tape delay cassettes in smaller versions, but for some reason this was never used in the classical electronic music world.

Dry & Wet Hire
These 2 terms are used in the professional rental business, a dry hire is when you just rent equipment as is, while a wet hire is when you rent equipment by the hour and the technicians to operate or erect the item with it.

Any company that supply equipment with slightly unusual technical requirements like a specialised editing station, or equipment where training will mean a huge difference in the time it takes to get it operational, like a mobile stage for instance, any idiot can erect one but a trained or experienced person will get it done in 1/5th of the time. In addition to having its own personnel or freelancers closely linked to the company going alongside the rented unit works as a sort of insurance for the rental company. You would for instance expect to dry hire a signal processor or a video camera, but it might get difficult to get mobile stages or very complex specialised video or audio workstations on anything but wet hire.

You will also find that if you are starting out in the business that companies will insist on a wet hire initially but will be more amenable to giving you dry hires when you have proven yourself financially and technically.

Dual action truss rod
A Truss Rod intended for guitars or similar stringed instruments that allows you to make both concave and convex adjustments to the guitar neck, ordinary truss rods do not compensate for a lack of backbow because guitars usually do not suffer from a lack of relief.

Consult a manual or the manufacturer of an instrument before adjusting a dual action truss rod, unlike most other rods to get relief you usually turn a dual action rod clockwise, i.e. the opposite to a normal rod but this may vary from manufacturer to manufacturer and as over-tightening a rod can damage a neck, so hunting down info before you start is highly recommended.

Dual Mono See --> Mono

Dumping
Dumping is the practice of selling industrial goods below manufacturing and distribution costs in order to gain market share or to hurt your competitors. This is illegal in some circumstances and in most countries where it is illegal it falls under anti-competitive or anti-monopoly legalisation, but in the USA there is a separate set of anti-dumping legislation composed in the 1980's specifically targeted at Asian manufacturers of consumer goods.

In reality dumping is nowhere as common as some politicians and media outlets might want you to think and actually almost unheard of in the real world, so much so that it can be thought of as a political myth. The reason for this simply that most companies are not that keen on loosing lots of money on the hope that their competitors will hurt even more, since the hurt of their competitors is by no means a given thing and any market share gained in no way assured to be permanent.

As far as the law is concerned with a few exceptions anti-dumping legislation's are mostly used as a political tool which can best be seen by the fact that in most cases when it has been invoked it has been used against groups of companies from certain countries and not against specific companies and their trade practices.

The USA government for instance used the anti-dumping laws from 1984 as a leverage in trade talks it had with the Japanese Ministry of Trade and Industry (MITI) resulting in the Japanese agreeing in 1987 to vacate certain computer related market segments and even ban the free distribution of software that some Japanese universities had partly financed (strange but true, see TRON OS). It has even been suggested that the 1984 law was pushed through explicitly for that purpose, although that is a bit on the paranoid side and it is more likely that law was how local politicians responded to pressures from companies that found it difficult to compete with low-wage Asian countries or Japanese manufacturing technologies that were more productive than their own.

In all instances when blocks of companies from specific countries have been targeted there have in fact never been a case of actual evidence being shown for dumping practices, all evidence has been at best circumstantial and used artificial value indicators as the primary proof rather than intent, but losing money is neither illegal nor immoral, merely unfortunate in most cases and difficult to use that as proof since there is a need to show intent. Most successful cases of prosecution against companies for anti-competitive behaviour in the last 20+ years have been on the opposite end of the scale, companies have been artificially inflating prices through illegal collusion and other techniques, but the same problem exists there, making money is not illegal so any anti-competitive authority has to prove action and intent.

In all of the cases where the 1984 USA legislation was used the companies that bothered to go to the Court of International Trade won their cases (the fines in 1 or 2 cases were too small to makes some companies bother), this left a residue of companies that have had their name cleared before an international court of but are commonly referred to in articles, postings, books, news items and even in university level textbooks as having been found in a court of law to be guilty of unfair trade practices and often of some sort of evil conspiracy to defraud in collusion with sundry organisations, usually industry ministries of foreign countries or "shady industrial organisations", which at a closer look turn out to be the local Rotary Club.

Duplex
Duplex means literally "of 2 parts", in technical circles this is used to indicate a device that can handle traffic 2 way's or input and output of a signal. This gives rise to the rather strange term Half duplex but that indicates a device that can act as both a transmitter and a receiver of signals but not both at the same time so traffic that is going one way has to wait for traffic from the opposite direction to halt before it can proceed, Full duplex devices can handle traffic 2 ways simultaneously, an alternative term is transceiver and is more common in networking terminology. A number of older digital audio processors are only half duplex, but that is becoming rare.

Dynamic Range
In Hi-Fi : The difference between the highest and lowest volume that a piece of equipment is capable of reproducing, measured in decibels.
In Music : The difference between the loudest and the quietest passage of music, measured ditto, as modern pop music is compressed to death in to make it more "radio friendly" this is meant to be as close to 0 as possible.

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