Saturday 30 November 2013

Geeks of the Week!

The Radio Channel (DARC) is a high-rate (16 kbit/s) standard for encoding data in a subcarrier over radio station broadcasts. Decoder software for DARC does not exist, according to search engines. To read the actual data frames, I'll have to acquire block synchronization, regenerate the pseudorandom scrambler used and reverse its action, check the data against CRCs for errors, and implement the stack of layers that make up the protocol. The DARC specification itself is luckily public, albeit not very helpfully written; in contrast to the RDS standard, it contains almost no example circuits, data, or calculations. So, a little recap of Galois field mathematics and linear feedback shift registers for me.

 Doctors Who?  Or, perhaps ...
Stephen Hawking.

In fact, neither. These are the pearls of dubious wisdom that drop from the lips of ...
... the delectable Oona Räisänen!

Oona has a strange hobby; she decodes computer data as broadcast in radio signals and telephone lines; in a way she's an upmarket hacker. And she comes from Finland.

In company with fbb and myriads of other sad and slightly silly souls, she writes a blog ...
... telling the world at large (well, those bits of the world that can understand what she's prattling on about!) what she has just decoded.

And so to Helsinki bus services.
Public transport in Helsinki consists of bus, tram, metro, train, and ferry services. The system is managed by Helsinki Region Transport (HSL/HRT) and covers Helsinki, Espoo, Kauniainen, Vantaa and the outlying Kerava, Kirkkonummi and Sipoo.

Oona discovered that information for the real time electronic displays ...
... was being sent as part of a VHF radio signal via a Data Radio Channel; in other words carried piggy-back in the spare bandwidth of the speech and music signal that you hear on your tranny.
It's that fuzzy stuff at the right hand end. [fbb  apologises for any technological inexctitudes; there is a link to Oona's blog at the end of this post if you wish to get it right!]

Cleverly she was able to decode these signals and she found, firstly, route number and destination names ...
Here's a chunk of the map for the 23N:-

Place names are shown in in Finnish and Swedish.

Ruskeasuo (ruots. Brunakärr) on kaupunginosa Helsingin kantakaupungin luoteiskulmassa Mannerheimintien molemmin puolin. Peruspiirijaossa Ruskeasuo kuuluu yhdessä Laakson ja Meilahden kanssa Reijolan peruspiiriin. Ruskeasuon asukasluku on noin 6900 (1.1.2008) ja työpaikkoja alueella on noin 6100 (31.12.2005).

Languages are fascinating. There's a word with four "u"s in it - kuuluu. fbb thinks (rubbish, google translate thinks) that it is part of the verb meaning "belongs to". Maybe stick to English Wikipedia?

Ruskeasuo (Brunakärr in Swedish, verbatim "Brown swamp"), is a neighbourhood of Helsinki (Helsingfors in Swedish), about 3 kilometres north of the city centre.

Then she found evidence of times ...
... and, intriguingly, a sentence in German, "Bus 61 nach Flughafen aus Haltestelle 1" (Bus 61 for the airport from stand 1)! As with all geekish activity, the fun is in the searching and sorting and Oona has concluded her project by making her own real time screen.
Of course, conspiracy theorists will be aghast to know that facilities are readily (?) available to decode stuff that flies invisibly through the air. Link this to the recent news that the USA is listening in to phone calls and emails from supposedly "friendly" politicians and nothing electronic is safe or sacred.  Spookeeee!

Talking of Doctor Who and Geeks. Some dedicated whovian has posted a video on YouTube showing every version of the show's introductory captions over the past 50 years. This you must see!

Geeky or what?

Then there are sad, sad people around who seem to enjoy such esoteric activities; people who can tell you that the lowest bus route nunber ever used in Sheffield was ...

and the highest for a normal daytime service was ...
fbb, a geek? Perish the thought!

And, of course, the next Doctor Who is to be Peter Capaldi. But he has already appeared in a story about Pompeii ...
... nothing to do with his forthcoming assumption of the Doctor's persona.

Or, maybe ...
fbb is much indebted to No 2 son for guiding his old man to the Oona blog (read here). No 2 does clever computer stuff including writing games and designing flashy publicity for a caff ...
... so please feel free to pop in and enjoy. Teo's is just round the corner from the bus station ...
... in San José del Cabo; MEXICO!

 Next bus blog : Sunday 1st December 

1 comment:

  1. I was pleasantly reminded of the period when, as a young teenager, we would watch the screen change from Doctor OHO to his real name.

    Thanks to FBB, I can now pin down that period in my 'development' to the years 1963-1967.

    Wow, the things you learn............!