MaBell Project Plan v2: A Low-Voltage Phone #

Plan: MaBell Bluetooth Gateway: Project Plan · Previous: v1: On the bench · Next: v3: Line voltage and a real bell

A real telephone makes and receives calls through the gateway, on a 5V DC loop with no high-voltage hardware. Status: next. Its definition of done and tasks are written when it becomes current, with what v1 taught.

📄 Build guide: notebook/build-guides/low-voltage-test-rig.md

Scope #

A cheap corded phone with a tone/pulse switch replaces v1’s stand-ins:

• Call tones: played into the phone’s earpiece over the loop, and judged again for authenticity there.
• Ringing: still a piezo or LED; a real bell needs line voltage (v3).
• Hook detection: the phone’s own hook switch, sensed through the loop current.
• Rotary detection: the phone’s pulse dial, sensed through the loop current.
• DTMF detection: the phone’s keypad tones, AC-coupled from the loop into the ADC.
• Call audio: through the handset, and how much echo the loop brings.

Not in v2: line voltage, a real bell, a vintage phone (v3).