I will describe some ways in which these transgressions occur. Readers can then make informed decisions, as to the safety of instruments & equipment they own or use. I will point out that some so called "safety features" are anything but.

A number of means are available to reduced the chance of painful or lethal electric shock. Some are specified in various British & international standards. Professional & industrial equipment generally used to comply with these standards. Most domestic equipment at one time had very limited safety requirements.

Manufacturing costs were the main concern back in the days when electronics meant valves (tubes). Televisions needed many valves & an expensive Cathode Ray Tube (C.R.T.). They dissipated a lot of power, to save money the large, expensive, mains isolating transformer was dispensed with. The metal chassis was thus live to the mains, safety considerations were limited to restricting access to this chassis.

British Standards existed governing the size of ventilation slots, so small children could not poke their fingers in. Bureaucrats writing these standards seemed unaware that curious little children could insert metal objects, accidents, frequently fatal, were common. Some radios also had no mains transformers, with live chassis. The remainder usually had a two core lead with no earth provision.

The entire domestic electronics industry was geared up for the production of these dangerous devices. Complete ranges of valves were designed & produced in huge numbers. Their heaters had a common standard current, with different Voltages, according to power requirements. C.R.T.s were produced to match. Lower heater current valves were produced for radios.

All heaters could then be wired in series, sharing a common current. The total of all heater Voltages was designed to be as close as possible to the mains supply. Any shortfall was made up by a wirewound resistor, usually called a 'mains dropper'. This often had a number of taps, for different mains Voltage in various parts of the country. Mains across Britain varied between 200, 220 & 240 Volts.

Professional & industrial equipment was built to last, rather than be cheap to buy. Employers were also concerned about possible insurance claims from injured staff or their relatives. At a time of full employment, replacement staff were in short supply, so safety was much more of a consideration. Such equipment was almost invariably housed in an earthed (grounded) metal case & fitted with an isolating mains transformer.

When transistors evolved sufficiently to take over from valves, safety of lower cost equipment improved. Solid state circuitry was more delicate & required low Voltages. So the use of mains transformers became necessary, together with earth connections to reduce static. Ironically it was the needs of new technology that made electronics safer, not any concern for those using it.

Even televisions eventually became all transistor, apart from the C.R.T. The lower power requirements of solid state circuitry made an isolating mains transformer cheaper. So safety improved dramatically, most radios became battery operated, with mains power an optional extra. That was then, now things are very different.

The original BS 1363 specification describes a standard mains connector system including a safety earth pin & usually a fuse. This is the ubiquitous domestic 13 Amp' system that we are familiar with. Unfortunately a few variants have been allowed to creep in over the years. In particular when using so-called 'double insulation'.

British Electrical Regulations. Classes of Portable Electrical Equipment.

Ron Lebar's (Alpha Entek) Safety Rating.

Class 11, double insulated, simply uses two layers of insulation. Internal "functional" insulation separates mains conductors from one another, an outer "safety" layer then acts as a barrier to outside contact. For a shock hazard to occur, both layers must be breached. This however is not as difficult as it seems at first glance.

In addition to musical instruments the majority of portable home appliances fall into this category. Historically domestic safety has had a low economic priority. Take kitchen appliances as an example, the relevance to music safety will become clear later.

I think it is safe to assume that in cooking, water is a common ingredient. Therefore it is likely that kitchen tools will get wet, food mixers for example work with water based substances. Double insulation relies on an outer layer of plastic, wet plastic is no longer an insulator. Also in kitchens are water filled sinks, often made of metal, enough said, life is cheaper than profits.

The same is true of hand held power tools, often used in kitchens, bathrooms or outdoors. Even cordless tools require a charger, here the double insulation is particularly suspect. It is often child's play to touch the charging contacts, reducing it to single insulation, class 0. Not allowed for sale in the U.K., yet they are everywhere.

Many electronic musical instruments, including many 'professional' types, are placed by their makers in Class II, usually carrying the double square symbol to indicate they are double insulated. With a two core mains lead, often attached or with a 'figure of eight' connector.

To be safely double insulated requires two levels of insulation for protection from the mains. The only way this can be provided is to use a fully insulated case, with no external access to internal circuitry. The internal circuits have only the insulation of the mains transformer windings, for isolation.from the supply mains.

An instrument built in this way is unusual, with limited usefulness in today's era of instrument & equipment communication. It will still be vulnerable if a drink etc. is spilt over it, a common occurrence at events.

Instruments used by musicians usually require external connections to the internal circuits. For amplification, recording, MIDI, control pedals etc. Thus such instruments, if they have a 2 core mains lead, are in most cases actually 'single insulated', 'Class 0', with a safety rating of '0'.

This is the mains input area of a typical example. It is a respected professional keyboard with the double square symbol. The mains switch & "figure of 8" connector are clearly single insulated from the black metal case. As are the single bobbin mains transformer's bare primary pins.

Most professional instruments, especially from Japan, have a metal or part metal case. With mains components mounted on this metal work. Some have an earth provision, but many are classed by makers as double insulated. Yet it is obvious, if any mains component is mounted on an exposed metal panel, that it is single insulated. Many have a mains connector, switch, fuse, Voltage selector etc. mounted in this way.

If the single layer of insulation on any of these components is compromised, posibly by rough handling, the chassis becomes live. They are Class 0, with a safety rating of '0', ZERO. Yet they seem the most common type around. Complete with the double square mark to give confidence, as in the instrument pictured above.

Has the instrument you use got a 'figure of 8' mains connector on a metal panel? Think about it, what will happen if the lead gets tripped over, the connector breaks but still works? You have a gig to finish, an attentive audience & no spare keyboard. Do you pack up or continue?

Some will say the instrument is safe, because it gets its earth from the mixer or amplifier in use. A jack lead is not designed to carry high mains current safely to earth in the event of a short. Nor is the input circuitry of most modern amplifiers or mixers. If the worst happens, it may merely blow the earth tracks off the printed circuits, an expensive repair or a new piece of gear...

But what if someone was holding a microphone in one hand & something connected to that amplifier, mixer or keyboard in the other? It has happened many times, often with fatal results. The odds may be against it, but who wants to play such odds?

Our Sky Digital satellite television decoder frequently "hung up". It has no reset button or power switch. So the only way to re-start it, is to pull, then re-insert, its mains connector.

Some time ago it hung while my wife was alone in the house. She performed the re-start trick and got an electric shock. Sufficient to make her lose balance and be injured.

Upon checking the decoder, I found its case to be appreciably 'live' to mains. It has a metal case and a two pole figure of eight mains connector. The television also has a figure of eight mains connector, but a plastic case. The lead to the telephone network, for Sky software updates, does not provide an earth, as we are on optical cable. A wired internal telephone system would ALL become live, ours is cordless, which is fortunate for us.

Obviously I was very annoyed. Sky Digital did not bother replying to my E-Mails of complaint. Presumably they feel they are too big to be hurt by us. So we simply cancelled the Sky account and installed our own motorised dish. Now we can watch anything we want, on any satellite, without paying a distribution company on top of the licence. I strongly recommend anyone who cares to do the same.

There are other design problems with such decoders. 1: Excessive supply drain when on standby, aggravated by the lack of a power switch. This is particularly relevant in light of today's environmental concerns and will be covered in more detail on our 'Design Standards' page.

2: The use of cheaper 'dynamic RAM' for the channel memory. This 'forgets' all data when power is removed, so if we did provide a switched supply for the decoder, it would take 15 minutes or more to re-scan the satellite channels each time it was switched on. These days non-volatile RAM or Flash RAM are reasonably priced so why are they not used by the cable companies and Sky? Our private satellite decoder uses such memory, so we use a remote controlled mains distribution board. This switches power, using the TV's remote control, highly recommended and readily available.

More will be written as time permits...