It can play ISO files as though they were DVDs. First, mount the image;
$ sudo mount -oloop /path/to/dvd_image.iso /media/dvd
Then to play the first programme from the disc;
$ mplayer -dvd-device /media/dvd dvd://1/

Now, the discs created on my standalone DVD+R/RW recorder are a bit weird, in that the .vob files on the disc don’t correspond with the recorded programmes. So I can’t save an individual programme just by copying its .vob file; meaning, if I wanted to keep a whole series together, I would have to record all the episodes on the same disc.

But mplayer has an option, -dumpstream which simply extracts the MPEG data from the source and saves it to a file. The default filename is stream.dump but you can specify an alternative filename with -dumpfile /path/to/somewhere. And without having to display anything, it isn’t constrained by the frame rate. Don’t be alarmed by the “Core dumped ” message — that’s just hacker humour.

So we can extract the second programme from a disc (or a mounted ISO image), and save it as an MPEG file, with a command like the following;
$ mplayer -dumpstream -dumpfile /path/to/saved_file.mpg -dvd-device /media/dvd dvd://2/
Remember, this is the actual MPEG data from the disc, so it’s already a DVD-like MPEG2 file; and therefore suitable for burning to disc with your favourite DVD authoring application. Or just saving onto one of those USB external hard drives with a built-in media player.

Don’t forget also the excellent ffmpeg, which can convert nearly any media file format to nearly any other media file format.

Your gas meter measures cubic metres of gas flowing through it. (The old ones used to measure cubic feet; but the gas companies switched to proper measurements longer ago than the lifetime of a gas meter, so they should all be cubic metres by now.) But your bill is calculated on the number of kilowatt-hours of energy liberated from the gas.

On your bill, there will be a calculation such as this:

metric units used 239 * calorific value 39.3572 * volume correction 1.0226400 / convert to kWh 3.6 = gas used in kWh 2448.43

So what do the figures mean?

• metric units used is the number of cubic metres of gas measured by your meter.
• calorific value is the number of megajoules of energy in a cubic metre of gas, at some specified combination of temperature and pressure.
• volume correction is a “fiddle factor” to account for seasonal variations in air pressure and temperature. When it’s cold, the molecules are more densely packed, so you get more energy in the same space. When the atmospheric pressure is low, the gas molecules are free to jiggle about more, so you get less energy in the same space. Each molecule contains a certain amount of potential energy stored in the bonds between atoms. So the calorific value depends on pressure and temperature, which is why this calculation is required.
• conversion to kWh is because there are 3.6 megajoules in a kilowatt-hour. (A watt is one joule per second; there are 3600 seconds in an hour. Kilo means * 1 000 and mega means * 1 000 000.)

Given these figures, you can work out how many kWh are in one cubic metre of gas, simply by doing the same calculation for 1 metric unit used. According to the above, it is 11.23 kWh per m³; but this figure may well be different for you, as the volume correction is seasonally-dependent.

But that’s not the whole story. The price per kWh depends on how many units you have used, with the first few kWh each day being more expensive. There will be a section like this:

2448.43 kWh used over 103 days
First 756.00 kWh @ 6.846p = £51.76
Next 1692.43 kWh @ 3.275p = £55.43
Total cost of gas used = £107.19

The higher rate applies to 756.00 kWh over 103 days, and adds an extra cost of 3.571p per kWh. As long as we actually use up all the “expensive” kWh, we will end up paying a fixed extra amount each week. If we are allowed 756.00 kWh in 103 days, then that is equivalent to 756.00 * 7 / 103 = 51.38 kWh in 7 days; which will cost us an extra 51.38 * 3.571p = £1.83 on top of what they would have cost if we had only been paying 3.275p for them.

Meanwhile, one cubic metre of gas on the meter gives us 11.23 kWh and so costs us 36.78p. So, our weekly bill will be equal to £1.83 plus 37p for each m³ of gas used.

Simples!

If you ask your gas supplier nicely they will send you a payment card, which can be used at local shops to make payments towards your gas bill. All you need to do is to work out the cost of the gas you have used each week (basing it on the figures from your last bill, which probably won’t be the same as mine), and round it up or down to the nearest whole pound.

Analogue radio, and even analogue colour TV, were much closer to Universal Comprehensibility than their digital equivalents.

Building a MW / LW radio receiver is not hard — years ago, nearly every schoolboy did it. Building one that works well under all circumstances is tricky, but amplitude modulation — which is used on the medium and long wave bands — is basically easy. You have a high-frequency carrier signal, which you make get weaker and stronger in time with the audio signal getting weaker and stronger. You feed this into an aerial system, and invisible electromagnetic waves travel away from it in all directions. The person listening has a tuned circuit, which lets through just the frequency of your carrier signal; a rectifier, which converts the high-frequency alternating current into direct current (which is still rising and falling in time with the audio signal); and an amplifier, which boosts the signal enough to move a loudspeaker cone. That’s a bit of an oversimplification, but I don’t want to lose my audience.

Frequency modulation is a little bit harder. This time, instead of varying the strength of the carrier signal, you vary the frequency Where your oscilloscope trace is above the zero line, you move the peaks closer together; where it goes below the line, further apart. So the frequency of your carrier signal is changing. This isn’t as big a problem as it sounds, because most tuned circuits aren’t perfect; so the one in the receiver will let through frequencies that are within a certain tolerance anyway. You also need a different kind of detector, which responds to changes in frequency as opposed to amplitude; but once you have built that, you can make use of the same power supply, amplifier and loudspeaker as before.

Doing it with pictures involves another layer of complication since there is no single, universally-accepted way of representing a picture as an electrical signal. And that’s just in mono — don’t get me started on the various ways people have actually transmitted colour pictures. In practice, though, agreements were thrashed out between governments, broadcasters and setmakers on a country-by-country basis, so all the TV sets in any given country worked on the same broadcast standard. And home video equipment works to national broadcast standards precisely so that an ordinary television set can be used to view home recordings.

Still, the fact remains that anyone with the right knowledge can build a radio transmitter. (Actually using it is another matter; if your signal travels far enough to interfere with other users, you can expect to end up in court. Not much is likely to happen if you build a small, low power transmitter and nobody finds out about it. And if the Rule of Law has already broken down …..)

But digital broadcasting is a whole other kettle of fish. Even building a digital receiver requires access to proprietary technologies (and this includes mathematical operations over which some people claim to hold patents!), although they may be available under what appear to be generous licencing terms. This is only because the big corporations are aware that in order to sell transmitters, receivers need to be almost given away. Building a transmitter is what requires access to the seriously expensive stuff, and that’s what they aren’t going to let Our Sort near.

Call it paranoia on my part if you like, but there’s no denying that wholesale adoption of digital broadcasting will end up making it nigh-on impossible to start an underground radio station — and in so doing, will deprive The Population At Large of a potentially extremely useful weapon against a corrupt government.

Esse 100 SE

Here’s a picture taken without the flash, using just the light from the fire:

Esse 100SE -- by own light, no flash

And I needn’t have worried; she loves it!

Anyone who has ever tried generating their own electricity will know that these bulbs are stupidly wasteful. A 100W bulb kicks out some 95W of heat. It’s surprising really, what with the distinction that has to be drawn between (for example) strawberry flavour, strawberry flavoured and strawberry lest the consumer be unaware how little fruit the product contains, that they’re even allowed to call them “light” bulbs at all! Heat bulb would be a much more accurate description!

Every person who has bought a 100 watt filament bulb to use for general illumination instead of a 20 watt compact fluorescent bulb is needlessly pissing 80 joules of energy up the wall every second the thing is on, using up fossil fuels that won’t ever be available again. Add up all those 80s and you could probably take a whole coal- or gas-fired power station out of service.

Of course, the 20 watt fluorescent is still putting out 15 watts of heat, so there’s room for improvement, and there does need to be a recycling scheme set up — but since compact fluorescent lamps contain enough valuable materials to be well worth recycling if you can get enough of them together, this is pretty much inevitable.

I’m looking forward to seeing the next generation of LED-based lamps.

Unfortunately, it’s meant to be a surprise for someone, so I can’t mention what it is until that person returns from where they are. I can’t even mention who that person is, or where they might be coming back from, in case they are reading this and work out who I mean and what I’ve had done. In fact, I think I’d better stop now.

Some jaw-droppingly bad blunders have been made with voting machines. One often-proposed idea is to issue voters with a receipt. This is an exceedingly bad idea. There is nothing to stop the machine from accepting your vote for candidate A, issuing you with a receipt for candidate A, and then recording a vote for candidate B. You might be able to work out from examining the hardware and the software that that was what it was doing; but of course, they embody confidential trade secrets of the manufacturers.

Even if the USA were to make it law that voting machine manufacturers must publish their blueprints, schematics and software listings to allow independent scrutiny (by the tiny minority of the population who can make sense of such information), how can you be sure that the machine that accepted your vote on polling day was actually built in accordance with those plans and running that software?

Now Imagine this on a notice board in a workplace:

All workers taking time off to vote will be expected to show their receipt proving that they voted for the factory owner’s brother-in-law under penalty of dismissal.

Voter receipts do nothing to prevent the following scenario:
Suppose Candidate A receives 500 votes, B receives 390 and C receives 110. These are the actual votes, remember. The announced result, however, is A 380, B 500, C 120. (Note that those figures are not so far out as to be utterly implausible. If they wanted to get a candidate elected in the face of very strong opposition, they might have to field a few extra candidates of their own just in order to split the vote.) You voted for A. You go with your receipt to the Town Hall to check how your vote was recorded, and are correctly told you voted for A. And that’s as far as you can take the matter.

Even if all 499 of the other people who voted for A go and check, they’ll be told — rightly — that their vote was for A. And because (1) they all go in one at a time to check their vote, and (2) there are also many B- and C-voters in there, not one single one of the A-voters will be the slightest bit the wiser that there are really 500 of them, as opposed to the 380 that was announced!

You could only determine that something was amiss if all those A-voters produced their receipts for Candidate A at the same time. And in reality, the proportion of voters who will actually bother even to check their vote will be minuscule.

Sacrificing voter anonymity altogether does not prevent the following scenario:

Suppose we extend the above scenario a little, and sacrifice the secrecy of the ballot in the name of being certain that votes were counted correctly.

First, they need to compile a list of everyone and their wider social network: their friends, neighbours, family, work colleagues and so forth. This isn’t half as big a task as it sounds, what with the likes of Facebook doing all the donkey work for them.

The results are published on the Internet; subject to DRM, of course. The DRM is partly a blind. Every voter must enter their own unique code in order to see the election results. In return, they get to see everyone’s name, address and who they voted for. The results can’t be printed, nor left on display for too long (hence the part of the DRM that isn’t a blind), to guard against misuse. That should reassure the voters a little (but not much, since anybody with enough money may still be able to pick up a copy by other means.)

They can announce whatever the hell result they like (as long as it’s favourable to them and represents a plausible turnout); it need have no correlation with how people actually voted.

The clever bit: Every voter gets to see their own vote, and the votes of their social network, exactly as they were cast; however, the votes of others outside their social network are altered to make the totals up to the desired figures. (This is why it is necessary to enter a unique voter ID code to access the list: everybody needs to be shown a slightly different list. DRM is a good front for this.) So I can see online that my grandad and my mum both voted Tory, my aunt in Porthmadog voted Plaid Cymru, my ex-coal-miner uncle voted Labour and that dippy tart down the street with the blue hair voted Green Party. All these people would also see my vote recorded correctly, if they looked, and nobody is surprised.

And the only way to demonstrate any wrongdoing is to ask a lot of strangers who they voted for, which comes with its own attendant risks. (I voted for the punch in the face party, anyone?)

Voting machines are the problem in and of themselves. Hand counting by the candidates themselves, or their representatives, exploits an existing adversarial relationship. None of them trust any of the others, so the only way they can agree on a result is if it is correct.

The first intention was to use a mechanical time delay switch, but this was found to be a rather costly solution.

The lights themselves were modified from 3-LED, battery powered push lights obtained in packs of two from a pound store (I frequent such places, searching for anything with white LEDs to use in my experiments!) The modification was simple but fiddly; entailing some track cuts to rewire the LEDs from a parallel to a series circuit and bypass the switch, and a resistor change. The timer itself was built inside an MB2 plastic enclosure with a pushbutton switch.

Circuit operation is as follows:

When SW1 is operated, C1 charges quickly via R1. Current flows through CR1 into the LEDs and the rest of the circuit. IC1, LM2903 is a dual comparator (only one half is used). The voltage at pin 3 rises higher than the voltage at pin 2, and so the output pin 1 goes high. R6 is required because the 2903 has open-collector outputs. It should be omitted if a dual op-amp such as LM358 is used instead. TR1 turns on and RY1 pulls in. By the time SW1 is released, the LEDs and circuit are now receiving power via RY1. The voltage at pin 3 falls until it drops below the voltage at pin 2, causing TR1 and RY1 to turn off. The voltage on pin 2 rises, to ensure TR1 will not turn on again before the relay contacts break fully.

The timeout is set by R2, R3 and C1. These values give approximately a 3-minute timeout with RV1 about a quarter of a turn clockwise, which was found to be plenty of time to complete the bin run. If more time is required, SW1 can be pressed again to restart the 3 minutes.

Note that CR1 and SW1 have to withstand the full startup current of the load (here, four series strings of three LEDs at 30mA, so well within ratings). To overcome this limitation, use a double pole relay: one pole switching the IC and coil, and the other pole switching the load. Alternatively, use a second relay (connected as the load on the timer relay) to switch the main load.

Now, while I’m not defending the BNP in any way, I have to say that I think the alternative would be much, much worse. Any law that managed to ban the BNP would effectively grant a governing party a veto over the election of any opposition party. Which part of that would not be wide open to misuse? If the BNP can be banned because of something objectionable in their manifesto, then why not the LCA? Why not the Greens, or the Lib Dems, or the Tories? Any legislation that had the power to kill the BNP would kill democracy, and such collateral damage is clearly unacceptable.

Better, I think, to sit this one out. One of two things has to happen. Either the BNP will (contrary to their manifesto) behave like human beings, and there will be nothing to worry about; or they will expose their true colours, and the popular support they successfully courted this time around will turn rapidly to resentment.

Most importantly, come the next election, people will be getting out and voting just to make sure that the BNP don’t get a seat anywhere really important.