ADR-0006: The device answers with light, never with sound

Context

Rafa: the device "only listens, doesn't speak, so communicates with lights / hardware."

Two things must be visible to everyone at the table: can it hear? and what is it keeping? The first must be trustworthy even if firmware is compromised.

Decision

Two separate lights:

  1. Mic-live dot — one small warm dot in the centre, powered from the mic rail (S-06). If the dot is on, the mics have power. Firmware can't turn it off.
  2. Rung ring — five segments around the dot, driven by firmware. Number of lit segments = rung (R3 = three segments). Count, not colour, so it reads for colour-blind people.
Situation Ring Dot
Recording at R3 3 segments steady on
Off the record (R0), listening for "back on" all segments off on
Mic slider off off off
Heard a lowering segments go out one at a time, top down, then a short haptic tick if held on
Heard "forget the last N minutes" ring sweeps counter-clockwise once on
Raise requested target segments blink for the objection window on
Objection heard blinking segments go out on
Returning to default after a conversation ends segments light slowly, one by one on
Didn't understand something addressed to it ("Goldfish, …") ring flickers twice on
Touched / picked up ring briefly shows retention: segments = weeks of gist remaining on
Reading (USB + button held) ring rotates slowly off (mics cut while reading)

Consequences

# ADR-0006: The device answers with light, never with sound

- **Status:** superseded in part by ADR-0008 (one dot per participant; brightness replaces the segment count)
- **Date:** 2026-10-12
- **Requirements touched:** P-03, P-04, S-06

## Context
Rafa: the device "only listens, doesn't speak, so communicates with lights / hardware."

Two things must be visible to everyone at the table: **can it hear?** and **what is it keeping?** The first must be trustworthy even if firmware is compromised.

## Decision
Two separate lights:

1. **Mic-live dot** — one small warm dot in the centre, powered from the mic rail (S-06). If the dot is on, the mics have power. Firmware can't turn it off.
2. **Rung ring** — five segments around the dot, driven by firmware. **Number of lit segments = rung** (R3 = three segments). Count, not colour, so it reads for colour-blind people.

| Situation | Ring | Dot |
|---|---|---|
| Recording at R3 | 3 segments steady | on |
| Off the record (R0), listening for "back on" | all segments off | on |
| Mic slider off | off | off |
| Heard a lowering | segments go out one at a time, top down, then a short haptic tick if held | on |
| Heard "forget the last N minutes" | ring sweeps counter-clockwise once | on |
| Raise requested | target segments blink for the objection window | on |
| Objection heard | blinking segments go out | on |
| Returning to default after a conversation ends | segments light slowly, one by one | on |
| Didn't understand something addressed to it ("Goldfish, …") | ring flickers twice | on |
| Touched / picked up | ring briefly shows retention: segments = weeks of gist remaining | on |
| Reading (USB + button held) | ring rotates slowly | off (mics cut while reading) |

## Consequences
- A legibility study is needed: can a stranger tell what it's keeping without being told? (`09-validation/plan.md`)
- Non-visual signal for people not holding it is unsolved (open question 8).