stecker

the cables are the key

28 HP

A cipher machine for notes. Each one goes through a plugboard, three rotors and a reflector and comes back as another, never itself, and the rotors step as you play. A cable between two of its twelve jacks swaps two notes; a second one set the same plays your tune back.

The STECKER panel: black, with three toothed wheels across the top in gold dots, each with a ring of pins and a hub under a knob, and a worn metal body below. Round each of the three knobs, I, II and III, a ring of twelve small marks of bare circuit board. Across the middle a row of twelve round lamps, named C to B. Under them twelve jacks named C to B in staggered rows, the plugboard. PLAIN and PRESS at the top corners, TURN and BACK jacks under them, STEP and KEY switches between the wheels, the TURN and BACK buttons under the outer wheels and NOTCH under the middle one, CIPHER and LAMP in the bottom corners. stecker at the top, daylight noise at the bottom.

Turn a knob: drag it or tap either side of it, roll the wheel over it or use the arrow keys; a double click puts it back. STEP and KEY click from stop to stop the same ways. TURN and BACK are buttons to press. Patch the plugboard: click a jack, then another, and a cable swaps the two; click a cabled jack to pull it out. The patches step on by themselves until you touch anything.

What you hear: a sequencer's riff into PLAIN and PRESS, CIPHER on the lead, the riff itself on the bass two octaves down, NOTCH on a crash, over drums and a dark pad. All made in the page as you listen.

example patches

The cipher, the rotors and the lights here are STECKER's engine, the module's own code, running in your browser; the sequencer, the voices and the drums stand in for a rack.

The cipher

A gate at PRESS is a key pressed: the note at PLAIN goes through the plugboard, rotors I, II and III and the reflector, back through the rotors and the plugboard, and out at CIPHER as another note, never itself. Through a second STECKER set the same, the tune you played comes back.

PLAIN: the note in, 1 V an octave, read a millisecond after PRESS rises.
PRESS: a gate in, a note each time it rises; unpatched, every new note at PLAIN is one.

The rotors

Each rotor is a scrambled wiring of the notes. The first steps as you play; each time it comes round past the top it turns the second a place, and the second the third, like an odometer. The marks round each knob show where its rotor stands.

I, II and III: each rotor's starting place, one for each note of the alphabet. Every place is another wiring: one click rewires the tune.
STEP: how often the first rotor steps. Its eight stops, turning clockwise: never, every 64, 32, 16, 8, 4 or 2 notes, and every note.
TURN: a button and a gate in: the rotors a place on. With STEP at never, a bar clock here changes the cipher every bar.
BACK: a lit button and a gate in: the rotors back to their starting places, so the tune repeats from the top. Its cap glows while they're away.

The plugboard

Twelve jacks, C to B. A cable between two swaps those notes on the way in and out, and every route through the rotors changes with it. Only pairs count: a jack cabled to two others is left out, and so is anything else patched in.

The alphabet

KEY: the notes the cipher uses, all on C. Its five stops, turning clockwise: the chord (C, E♭, G, B♭), whole tone (C, D, E, F♯, G♯, B♭), minor (C, D, E♭, F, G, B♭), phrygian (C, D♭, E♭, F, G, A♭) and all twelve.

Every note in is taken to the nearest note of the alphabet, and every note out is one of them, so in a scale the tune stays in key. An alphabet always has an even number of notes, as the reflector pairs them off: that's why no note comes out as itself. A cable to a note outside it waits until KEY lets it in.

What comes out

CIPHER: the note out, 1 V an octave, within half the alphabet of the note in, so the tune keeps its shape.
LAMP: a gate with each note, a millisecond after CIPHER, so the pitch has settled; the note's lamp lights with it.
NOTCH: a trigger each time the first rotor turns the second: a slow clock from the cipher's own count.

Inside

One board sits 10 mm behind the panel with everything on its front: the jacks, the knobs, both switches, both buttons, the 48 LEDs and the whole circuit, the USB-C in a notch in its right edge. Each window has its own white LED in a cell of a black printed baffle, so a lit lamp never lights the next note's. An RP2350 runs the cipher four thousand times a second and scans the plugboard a hundred times a second for cables.

The STECKER panel stepping: a lamp lit, each rotor's mark at its place, its knobs, switches and buttons on.

Drag it or use the arrow keys to turn it; click it to take it apart.

Specs

Format

Width: 28 HP
Depth: 20.8 mm behind the panel, plus the power plug
+12 V: about 40 mA dark, 75 to 95 mA in usual play, 190 mA at the most (estimated)
−12 V: about 2 mA (estimated)
+5 V: not used
Controls: 3 knobs, an eight-stop and a five-stop switch, two buttons (BACK lit)

I/O

PLAIN: 1 V an octave, −6 to +6 V, read to the nearest note 1 ms after PRESS rises; a 24-bit converter, calibrated; 0 V unpatched
PRESS, TURN, BACK: gates, high past about 0.9 V; unpatched, PRESS takes every new note at PLAIN as a key
CIPHER: 1 V an octave, −6.5 to +6.5 V (a note past that folds by an octave), 16-bit, calibrated
LAMP: gate, 0/5 V, a millisecond after CIPHER
NOTCH: trigger, 0/5 V, 10 ms
Plugboard: twelve jacks, C to B: a cable between two swaps them, counted within about 40 ms; only pairs count, and a jack with anything else in it is left out and comes to no harm
Every input: safe to ±12 V

Engine

Brain: RP2350, 4,000 steps a second
Decoding: exact through a second one set the same, for tunes within ±5.3 V
Light: 48 white LEDs, 125 frames a second
Power cycle: only the calibration is kept: the knobs and the cables are the key