## Spectrum analysis of Young Lust

Telephone World:

The telephone network at that time used multi-frequency (or MF) signalling almost exclusively when someone made a long distance call. These are similar to Touch-Tones, but use different frequencies and are used in a different manner. [...] Also in the analog telephone switching network, there had to be a way to tell the originating switch (or the switch that handled the billing) to start and stop the billing of a toll call. This was through the use of single frequency (or SF) tones. In North America, this was accomplished with 2600 Hertz, while in England this was accomplished with 2400 Hertz. (Some of you are already getting ahead of me...)
[...]

• 3:03.4 2600 Hz answer supervision -- duration .019 seconds pause .125 seconds
• 3:03.5 2600 Hz answer supervision -- duration .018 seconds
(Two bursts of 2600 Hz answer supervision, this means the call was going through two tandems. Again you hear the filters kick in)
...
• 3.13 MF toning starts
• Entire MF string is 'KP1' 0 4 4 1 8 3 1 'ST'

• KP1 duration .102 pause until next digit .015
• 0 duration .068 pause .050
• 4 duration .066 pause .052
• 4 duration .067 pause .051
• 1 duration ***.039*** pause .000

I call this the mangled '1' MF digit, because it appears the audio engineer working on this song must have cut and respliced the middle of the MF tones. The duration is very short 0.039 vs. 0.67 and there is no corresponding pause after the digit. It is instead jammed right up to next '8' digit. If you look at the wave you can tell it is a very ugly splice point.

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### 4 Responses:

1. Jeff Bell says:

So it’s a number in the UK (44) with an area code that starts with 1 and a number that ends with 831.

That narrows it down to less than 10^8 possibilities.

It’s probably a good thing that they edited out the middle of the number.

• Peter says:

Assuming of course that the telco-internal routing codes also followed E.164, although given the distinctive ring cadence and that Pink Floyd were British, it's probably a good bet that KP1 0 4 4 routed to the UK.

In 1979 when the song was released, +44 1 was London, which had seven digit local numbers, e.g. (01) 811 8181. Given the cut points, I'm not sure it's safe to assume that the number ends 831, just that it ends with a 1 and 83 appears somewhere in the middle. That there's a cut between 1 and 8, and 3 and 1 makes it seem unlikely that these are adjacent since why would they have made a cut if not to deliberately remove something? This is an actual cut with tapes and razor blades, not noodling around in Audacity.

So the most likely number is one of (01) x83 xxx1, (01) xx8 3xx1 or (01) xxx 83x1, with (01) 83x xxx1 and (01) xxx x831 being possible but unlikely. Relatively few director codes (the xxx in (01) xxx) would have been valid at the time, which reduces the search space somewhat. So we're looking at it being one of about 30–40,000 numbers, and most likely in a subset of about 15–20,000.

You're going to need a lot of tuppence coins to wardial that lot though.

• wunderhorn1 says:

And for what? Just to find out whether Mrs. Floyd is still shagging that speaker from the CND protest march?

2. Jeff Bell says:

That narrows it down to less than 10^8 possibilities.

It’s probably a good thing that they edited out the middle of the number.