Alarm about pool alarm

I have no quibble with your electronics capabilities but your front cover story in the September 2000 edition raises an alarm. Have a good look at the two photos of Georgia. In both you can see that the gate is unlatched! The photos show the end of the gate at least 100 mm from the latching post.

Primary safety (locking the gate) must be the first line of defence.

Brian Wilson,

Curtin, ACT.

Comment: blame the photographer. He lured Georgia through the gate. But her grandmother was standing poised, just out of the picture, ready to swoop. And she did!

CD Compressor should have had dual detectors

It was great to see the CD Compressor in the June 2000 issue of the magazine. However, I have some comments regarding the design.

John Clarke talks about the VCAs being "hifi laser trimmed units" but has only included one DC detector/control unit for both channels. It seems strange that he has not taken the better approach and kept the two channels completely separate.

By having two DC controllers for the VCAs, the signal of one channel does not modulate the other, if little or no signal is present. John’s single approach is as per the old dbx 117 and 119 units. Later units, from the model 128, I believe, had twin controllers.

The 3bx went the whole hog and had stereo 3-band active crossovers with separate DC controllers and VCA processing on each band. Having had experience in modifying 117 and 119 units to provide separate controllers for each channel, I can attest to the benefits of dual DC controllers. Getting these to track can be a bit of a fiddle when you have a compansion range of - infinity compression to +3 expansion on the 119, but as John’s design only has a range of -3 compression to 0 this shouldn’t be a major problem.

I should mention that the NE571 "compander in a chip" is still available and its small size would be beneficial in today’s cars where you have to shoehorn yourself in, let alone a box the size of John’s project. I know the VCAs of the 571 are not "laser trimmed" but for automotive or elevator music they might be an alternative.

Brad Sheargold,

Collaroy, NSW.

Comment: the idea behind this design was twofold and to some extent these conflicted. First, we wanted a better compressor than we had done in the past but we also wanted a very compact design which would work in cars. The latter criterion mean that we had to keep the parts count as low as possible and that meant only one detector. As it was, the requirement to use so many op amps was a real problem.

Electrical licencing debate

Well, I’ve read enough emotive "sparkie bashing" in the Mailbag to force me to put my five cents worth in. I’ll say first up that I detect a lot of sour grapes and venting of spleens arising from what was initially an issue regarding kits with mains wiring involved. I’ll also say that I believe some are using what they think is the "Parliamentary Privilege" of an electronics magazine to unfairly knock those in the electrical trade.

I am a sparkie myself, having enjoyed the huge window of opportunity such a trade offers for about 10 years now but before that, I was an electronics technician employed in the industrial electronics field. While I enjoyed many of the challenges in the game, and still miss some of those, I’m glad I had the persistence to pester my boss into taking me on as an apprentice electrician.

I was also cocky enough to think those four years of the apprenticeship would be unnecessary given my technical knowledge but I soon learnt there was a huge amount to absorb and take in regarding rules, regulations and safety. In short, it was a whole new world, ever changing and dynamic and it has been a constant effort to try and keep up with the changes.

I currently work at a remote mining site in the north-west of Australia where the electrical staff have to be up to speed on everything from domestic wiring to process control of plant to power generation to Austel Licensed communications work to radio communications work to high voltage work (up to 33kV here), all without killing ourselves or others or causing damage to the plant.

While I believe there is an issue with the mains-powered kit situation, I think the spillover into the attacks on the electrical trades in general is an example of very misguided and deluded elitism.

Peter Cairns,

Alice Springs, NT.

Health card is a silly idea

Your editorial in the October 2000 issue discussing a smartcard that stores the whole of a person’s medical record is a silly idea, for three reasons:

(a) there is no technology available which could reasonably be developed in the near future to make it possible and even if there was, the people in that industry would be wary;

(b) there are a lot of people who wouldn’t reasonably want it, and

(c) there are a lot more people who simply couldn’t do what they had to do if that were the way things were done.

There simply isn’t any card that can store that much info. Think about how few kilobytes are on a smartcard versus how many megabytes it would take to store scanned-in x-rays, with the high-capacity alternatives having to be reprinted in full each time there’s an addition. The closest we’d come today is a multi-session writeable DVD-ROM and who’s going to carry that around. And what if they lost it, or required emergency medical treatment in a situation where they didn’t have their records with them, like being taken unconscious to hospital after a car crash, or even were well away from home when they got sick?

There are a zillion reasons why anyone who has had to provide access to significant quantities of data at various locations but at the same time secure it and guarantee that it wasn’t lost would laugh at the idea of the customer carrying it around with them.

Sure, put certain vital or short-term info on a card or make it easily accessible by some other means but that’s all. I don’t mean to be negative, just realistic, so let me suggest an alternative:

(a) Connect all doctors, pharmacies and hospitals to the Internet, preferably by broadband or the fastest practicable other means;

(b) Encourage doctors and hospitals to store as much as possible of their records in computerised form accessible from the Internet, keyed not by name but by a private encryption key;

(c) Provide off-site managed data stores for doctors too small to operate their own data servers and managed backup;

(d) Allow access only to the data either by production of the person’s Medicare card, by a nominated family doctor or by authorised emergency medical personnel. There would also need to be penalties for doing it without good reason as is the case with criminal records.

Gordon Drennan,

Ultimo, NSW.

Comment: the health card is already possible and has been demonstrated. Credit card-size CD-ROMs are now available and DVD-ROMs in credit card size are equally possible.

Anyone in New Zealand
can do electrical wiring

I feel compelled to write concerning the electrical safety debacle that the members of the electricians’ cartel in Australia have ruthlessly perpetrated on their cousins in the electrical and electronics industries.

It may interest those in the electronics industry to know that anyone in New Zealand can legally do their own house wiring and house wiring repairs and modifications, as well as appliance repairs. This has been the case since 1992. Current legislation in New Zealand reflects the reality prior to its introduction of widespread do-it-yourself house wiring and appliance repairs.

There were no problems in legalising DIY electrical work in NZ because many New Zealanders have done their own house wiring and appliance repairs over so many years that they either know what to do or they can conveniently get the detailed information they need from relatives, neighbours, DIY books, etc.

The crucial aspect of the NZ system as it relates to prospects for reform of the Australian system is the number of electrical fatalities. The extremely low level of fatalities and the fact that none of the fatalities are related to incompetent house wiring or appliance repairs by householders makes the claims of the electricians’ lobby in Australia look ridiculous.

Safety is not the issue and never has been. The bigwigs in the electricians’ lobby know that ordinary people have done their own house wiring and appliance repairs in the United Kingdom and elsewhere for many decades but they persist with their propaganda about extreme dangers.

For the past year or so in Queensland there has been a blitz of expensive television "scare campaign" advertising by Energex, warning people that they are not allowed to do electrical work.

In Australia, on average, at least 100 people die as a result of rail accidents each year. Similarly, at least 500 die as a result of road accidents in each state in each year. The official figures from the AMA are that approximately 19,000 people die each year in Australia as a result of cigarette smoking and smoking-related diseases.

The New Zealand experience clearly demonstrates that the prospects of deaths due to electrical accidents do not warrant the ridiculously stringent regime that exists in Australia.

In Queensland, even electrical engineers who design complete power distribution and protection systems for multi-storey city buildings are not allowed to pull the wiring through the conduit in their own homes. When I checked with a number of large Brisbane electrical contracting firms I discovered that unskilled labourers pull the wiring through the conduits, ostensibly under the "supervision" of an electrician!

I am now retired but a little over a decade ago, just before I moved to Brisbane, I began the Associate Diploma in Electrical Engineering at St. George college of TAFE. I already had the Electronics and Communications Certificate from North Sydney TAFE but I was willing to do the electrical associate diploma because an electrician at building services told me that with the electrical associate diploma and a 13-week wiring course, I could get an electrician’s licence. I worked hard academically and came top of St. George tech for the first two stages of the four-stage electrical associated diploma course.

Luckily, one of my lecturers at St George tech, who was an electrical engineer for the electrical supply authority in NSW, alerted me to the reality that I could only get a restricted licence and I discontinued the course at the end of stage two.

The fact that I was a technical officer designing and building data acquisition and control hardware at Sydney University (for minicomputer
automation of psychological and physiological research), including the design and construction of power supplies, etc, meant nothing to the electricians at building services in NSW, and the situation is even worse in Queensland.

I am a member of Mensa but obviously neither a Mensa intellect nor proven knowledge and mechanical ability are enough to allow me to just pull the wiring through the conduit in my own home in Queensland, let alone wire up power points, etc. How long are engineers, technical officers and electronics service people going to stand by and allow this ludicrous situation to continue?

If engineers, technical officers and service persons effectively unite, we can put an end to these inequitable and totally unjustified restrictions on the performance of "electrical work".

Otto S. Hoolhorst,

Brisbane, Qld.