[fun] Weird electronic circuits collection

Different channels and different sets of programs. The license pays for the state channels. Independent channels need their own income - either by commercials, or by fees (for decoding the cable or satellite channels, or access to the net streams).

Of course that depends on the show. Some have recaps, some don't (at least in the versions shown here, which may have different cuts from those shown in the US).

Not in /any/ sense. These sort of state channels do not have adverts, and they do not have product placements in the shows they make. Some limited forms of product placement are allowed on external shows (such as films) shown on the channels - often there are rules requiring such programs to be marked explicitly for product placement.

That makes as much sense as most of what you write.

Why did they go to such level of complexity? Wouldn't a purely mechanical selector do?

Best regards, Piotr

Personally? None.

I would be /very/ surprised if you could drive past a 10 story block of flats, with a TV on in 85% of the apartments, and identify which ones were watching a particular channel (you are allowed to watch independent channels without a national TV license).

I am no expert in this field, but it does not seem a feasible task to me.

In the early days of television, where the percentage of TV owners was smaller, they were used less, and they were more common amongst affluent people with bigger houses and greater spacing - then I would believe that the detector vans might have been real.

The Compton Theatrone - for several reasons:

The use of spinning capacitors to generate waveforms.

The AC output of the capacitive generator was proportional to the DC voltage, so a simple RC circuit in the DC supply could be used to control the attack and decay characteristics. <

Exact tuning of each note without phase-locking them by using a long belt driving a different-sized pulley on each generator. <

Combining the waveforms in variable proportions to give a realistic harmonic structure. By varying the attack and decay of each harmonic independently, various effects such a bells could be obtained. <

A mechanical tremulant using an eccentric wheel pressing against a belt drive to frequency modulate the tone generators. <

The use of two separate power amplifiers for high and low frequencies to prevent cross-modulation in the output transformer (almost certainly designed by Williamson). The generators were in two banks, each connected to one amplifier only, so a crossover wasn't necessary. <

They had a mechanical selector in the earlier models, but it needed dozens of solenoids to allow it to be operated from a remote wall box (even though it was matrixed to reduce the number of components). Presumably the Tormat was cheaper to make and had the advantage of fewer moving parts to jam.

The Whiffle Tree used to control the swell shades of some pipe organs. An electro-pneumatically operated mechanical binary/analogue arrangement of wooden levers which gives 16 gradations of movement from 4 control inputs.

A similar binary arrangement of four bellows compartments in series is used in Aeolian organs for the same purpose.

"Never seen so many bloomin' aerials. The man said they could detect a purr at four hundred yards--and Eric, being such an 'appy cat, was a piece of cake."

Cheers

Phil Hobbs

Fair. UHF is difficult in urban areas anyhow, because you get reflections. But we do hunt with hand-held sniffer beams, including in cluttered RF environments. As always with enforcement, you don't need to catch many to stop most evasion though.

The Heathkit chart recorder used a pair of photoconductive cells as the chopper, they were alternately illuminated by two neon bulbs. You would think it could never work at any reasonable frequency, but I built one and it did.

I seem to remember we rewound the linear pot on one chart recorder using a piece of brazing rod as a former, wrapped in varnished toilet paper and rotated in a lathe. In the tool post we mounted a kind of travelling steady that fed in the wire under tension and we selected a screwcutting pitch on the leadscrew that would make sure the turns just didn't touch each other.

Yes, that's the point - you don't have to catch many people to scare others into following the licence requirements. In this case, the BBC and Post Office have been rather secretive about detector vans - the number of confirmed and published cases of van detection of people using TV's without a license is zero. It /may/ be that they have found people, who then paid the fine and bought a license. You would only get a good public record if the TV watcher challenged it in court - and certainly people /have/ done so ("I only watch ITV, you can't prove I watched BBC, and thus cannot insist that I buy a license"). Detector van evidence has never been used.

A neon bulb used as a leakage detector in the AVO capacitance bridge.

Mounting a ferrite-cored inductor, paralleled with an oscillator tuned circuit, in the magnetic gap of a Post Office relay frame. The current through the relay coil varied the saturation of the ferrite and fine-tuned the local oscillator of a VHF receiver.

The system was used in the very first radio microphone receivers for TV studios in the 1950s. They were made by Eddystone Radio (where I did my apprenticeship) and could follow a badly-drifting transmitter over quite a wide range.