### Royal Festival Hall condundrum

When I went to record Shift Run Stop at the Royal Festival Hall a few weeks ago I noticed that the display on the 5th floor lift was not showing 5 but a bit pattern. I snapped a quick photo and decided to look into it later:

And here's a close up of the top of it.

If you look carefully you'll see that there are 8 columns of on or off squares. I transcribed the squares with on = 1 and off = 0 to get the following list: 11111111 11000100 11011000 11101100 00000000 00010100 00101000 01001110 01110100 10001000 10011100 10110000 11000100 11011000 11101100 00000000 00010100 00101000 00111100 01010000 01100100 01111000 10001100 10100000 10110100 11001000 11011100 11110000 00000100 00011000 00101100 01000000 01010100 01101110 10001110 10110100 11001000 11101110 00000010 00010110 00101010 01010000 01111000 10001100 10110010 11001110 11101100 00000000 00100110 00111010 01100000 10000110 10011010 11000000 11010100 11111010 00100000 01001100 01101100 10000000 10010100 10101000 10111100 11010000 11100100 11111000 00001100 00110110.

Apart from the first item which is all 1s all the others have a right-most bit of zero. At first I thought this might be 7-bit ASCII (LSB first), but decoding that just gives a mess. Then I wondered if it was machine code, but I think that's unlikely given the fact that one of the bits is always zero. I don't think this is random data.

Here it is as hex with LSB on the right.
`ff c4 d8 ec 00 14 28 4e 74 88 9c b0 c4 d8 ec 00 14 28 3c 50 64 78 8c a0 b4 c8 dc f0 04 18 2c 40 54 6e8e b4 c8 ee 02 16 2a 50 78 8c b2 ce ec 00 26 3a 60 86 9a c0 d4 fa 20 4c 6c 80 94 a8 bc d0 e4 f8 0c 36`

And reversed:
`ff 23 1b 37 00 28 14 72 2e 11 39 0d 23 1b 37 00 28 14 3c 0a 26 1e 31 05 2d 13 3b 0f 20 18 34 02 2a 76 71 2d 13 77 40 68 54 0a 1e 31 4d 73 37 00 64 5c 06 61 59 03 2b 5f 04 32 36 01 29 15 3d 0b 27 1f 30 6c`

So, what could it be? I'm assuming that the display is showing something from either its internal memory or from the memory of its controller and that we are looking at consecutive memory locations (this could, also be incorrect).

Anyone else want to take a stab at this? Anyone know what company made the controller for the display or the lift?

The other thing that's odd is that there are lots of monotonic increasing sequences in the data. e.g. drop the ff and observe:
`c4 d8 ec00 14 28 4e 74 88 9c b0 c4 d8 ec 00 14 28 3c 50 64 78 8c a0 b4 c8 dc f0 04 18 2c 40 54 6e8e b4 c8 ee 02 16 2a 50 78 8c b2 ce ec 00 26 3a 60 86 9a c0 d4 fa 20 4c 6c 80 94 a8 bc d0 e4 f8 0c 36`

Nick Barnes said…
Take first differences.
Nick,

Brilliant! Why didn't I spot that?

Here are the first differences (mod 256):

255 197 20 20 20 20 20 38 38 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 26 32 38 20 38 20 20 20 38 40 20 38 28 30 20 38 20 38 38 20 38 20 38 38 44 32 20 20 20 20 20 20 20 20 42

And here are the numbers and their differences on two lines.

ff c4 d8 ec 00 14 28 4e 74 88 9c b0 c4 d8 ec 00 14 28 3c 50 64 78 8c a0 b4 c8 dc f0 04 18 2c 40 54 6e 8e b4 c8 ee 02 16 2a 50 78 8c b2 ce ec 00 26 3a 60 86 9a c0 d4 fa 20 4c 6c 80 94 a8 bc d0 e4 f8 0c 36
ff c5 14 14 14 14 14 26 26 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 1a 20 26 14 26 14 14 14 26 28 14 26 1c 1e 14 26 14 26 26 14 26 14 26 26 2c 20 14 14 14 14 14 14 14 14 2a

I wonder if it's possible to further dig into this and discover what causes that pattern?

### Your last name contains invalid characters

My last name is "Graham-Cumming". But here's a typical form response when I enter it:

Does the web site have any idea how rude it is to claim that my last name contains invalid characters? Clearly not. What they actually meant is: our web site will not accept that hyphen in your last name. But do they say that? No, of course not. They decide to shove in my face the claim that there's something wrong with my name.

There's nothing wrong with my name, just as there's nothing wrong with someone whose first name is Jean-Marie, or someone whose last name is O'Reilly.

What is wrong is that way this is being handled. If the system can't cope with non-letters and spaces it needs to say that. How about the following error message:

Our system is unable to process last names that contain non-letters, please replace them with spaces.

Don't blame me for having a last name that your system doesn't like, whose fault is that? Saying "Your last name …

### All the symmetrical watch faces (and code to generate them)

If you ever look at pictures of clocks and watches in advertising they are set to roughly 10:10 which is meant to be the most attractive (smiling!) position for the hands. They are actually set to 10:09.14 if the hands are truly symmetrical. CC BY 2.0image by Shinji
I wanted to know what all the possible symmetrical watch faces are and so I wrote some code using Processing. Here's the output (there's one watch face missing, 00:00 or 12:00, because it's very boring):

The key to writing this is to figure out the relationship between the hour and minute hands when the watch face is symmetrical. In an hour the minute hand moves through 360° and the hour hand moves through 30° (12 hours are shown on the watch face and 360/12 = 30).
The core loop inside the program is this:   for (int h = 0; h <= 12; h++) {
float m = (360-30*float(h))*2/13;
int s = round(60*(m-floor(m)));
int col = h%6;
int row = floor(h/6);
draw_clock((r+f)*(2*col+1), (r+f)*(row*2+1), r, h, floor(m…

### The Elevator Button Problem

User interface design is hard. It's hard because people perceive apparently simple things very differently. For example, take a look at this interface to an elevator:

From flickr

Now imagine the following situation. You are on the third floor of this building and you wish to go to the tenth. The elevator is on the fifth floor and there's an indicator that tells you where it is. Which button do you press?

Most people probably say: "press up" since they want to go up. Not long ago I watched someone do the opposite and questioned them about their behavior. They said: "well the elevator is on the fifth floor and I am on the third, so I want it to come down to me".

Much can be learnt about the design of user interfaces by considering this, apparently, simple interface. If you think about the elevator button problem you'll find that something so simple has hidden depths. How do people learn about elevator calling? What's the right amount of informati…