Picture of the Week: #46

The decorators have been and gone in our house, and the chaos has recently subsided. A bit, anyway. This has given my dad the chance to dig out some of his old music collection, and for the past week the house has resounded to Paul Simon, Randy Stonehill, Ry Cooder and Larry Norman. Now, this should give you a clue as to what on earth the above photograph shows. Have a guess, then look behind the cut to see if you were right.

If you guessed "part of a record turntable", you are both correct and very vague. Specifically, it's the edge of the turntable, right next to a little strobe unit. It's a very clever little bit of kit - the strobe flashes at exactly the right frequency so that when the turntable is rotating at exactly 33 1/3 rpm, one row of the reflective squares on its edge appears to be standing still. (It's the wagon wheel effect, if you're interested.) When the turntable is switched to 45 rpm, a different row stands still. It's an ingenious way of calibrating the equipment, and because it's not software-driven, it doesn't crash...