keeper

The lamp

• A row of 36 lamps sits at the focus of a real sheet of lens. Light a different one and the beam swings across the room. The row is one turn, laid out flat.
• TURN, the big knob, and its jack, 1 V/oct: twenty minutes a turn, for a whole set, up through a flutter to about 900 Hz. Eight seconds at noon.
• BEAM: broad, and the four outs are sines. At noon they're even swells that cross at half and always add up to one. At full, a needle: a sharp strike on each.
• CHARACTER, five stops: how the light reads. One flash a turn; two; three; two and one; and a light that stays on and goes out. Every out plays the same rhythm a quarter of a turn behind the last.
• CLOCK: patched, a turn takes a whole number of beats, TURN picks how many, and the lamp keeps to the grid.

Where you stand

• The pane stays black from everywhere but where the beam is. When it crosses your eye a band of the glass blazes, a moment earlier to your left, a moment later to your right. Two people in a room see it turn at different times.
• Each lamp lights a strip of the glass, and where the strip stands is where you're standing. Move your head a hand's width and it slides right across the pane. A wide beam is several strips with dark between them.
• A lens works both ways. A row of light sensors sits beside the lamps, so whatever the beam falls on comes back through the glass, and KEEPER knows where it was pointing when it did.
• Stand in the beam, or hold a hand out in it, and ROCK fires when it crosses you. Move, and the gate moves through the turn. Nearer, and it's longer.
• Put your hand over the pane and all four outs go dark. Take it away and they're where they would have been.

Out there

• FOG, and its jack: a real sheet behind the lens goes from clear to milk. The flash stops being yours: everyone sees the same soft light moving behind the glass. The four swells smear into one, the beam can't find you, and some nights a fog signal answers on ROCK, long gates that have nothing to do with the lamp.
• MADNESS, and its jack: how far it goes, and how soon. At noon it takes a minute or so; at full you can't count on anything. The turn goes uneven, the four drift off their bearings, the lamp sticks, lets go with a lurch and swings back, and sometimes it stops altogether.
• Far enough gone, it stops on you. It holds you in the beam and follows you if you go slowly, and the four outs follow your feet. Move quickly and you lose it.
• RELIEF, the button and its jack: the boat comes. Everything goes back to how it was, the turn from the top, and it all starts again. The button comes up by itself, the longer it's been.

What comes out

• NORTH, EAST, SOUTH, WEST: the lamp as seen from four bearings, a quarter of a turn apart, 0 to 8 V. No light, no volts.
• ROCK: a gate for as long as the beam's on something: the rock dead ahead, every turn, and anything else it's found.

Specs