Enclosure Design

The Ma Bell Bluetooth Gateway is designed to be housed in a 1U 19-inch rackmount enclosure. While the system provides support for legacy analog telephones, the internal design is built entirely with modern components. This section outlines the enclosure requirements and the design considerations for each face of the unit.

Front Panel

Ma Bell Gateway Front Panel

The front panel presents the device’s user-facing controls and status indicators. Key elements include:

  • Power button — momentary switch with integrated LED ring (e.g., 12V or 5V illuminated)

  • Status LEDs — at minimum:

    • STATUS (system operational)

    • BT (Bluetooth connection/activity)

  • Display — optional LCD or OLED panel (e.g., I2C 128x32) to show pairing status, call state, or diagnostics

  • Optional ventilation slots or mesh — depending on internal power supply heat dissipation

  • Rack ears — standard 19” mounting flanges with holes for rack screws

Back Panel

Ma Bell Gateway Back Panel

The rear panel must handle all external I/O and power connections. The final design includes:

  • PHONE

    • RJ45 jack wired to support analog telephone output

    • Center pair (Green/Red) provides Tip and Ring for loop current and audio

    • Outer pair (Yellow/Black) optionally carries 9V AC to power an illuminated rotary dial

    • Internal circuitry provides ringing voltage, tone generation, and rotary pulse decoding

  • BT/Wi-Fi Antenna

    • Single external SMA antenna connector

    • The ESP32-WROVER-IE uses a shared RF front-end for both Bluetooth and Wi-Fi

    • ✅ External antenna connector – The “IE” version includes a u.FL connector for an external antenna, ensuring strong signal coverage throughout the home

  • AC Power Inlet

    • Standard IEC 60320 C14 jack for main AC input (e.g., 120V/240V)

    • Powers the internal AC-DC supply that drives all system voltage rails

    • Internally fused and optionally switchable

Internal Layout Considerations

The enclosure must accommodate and isolate:

  • Custom PCB(s) for power delivery, signal conditioning, and ESP32 control

  • Audio coupling transformers and opto-isolated circuits

  • AC-DC power supply unit — potentially a small enclosed module or DIN-rail PSU

  • Voltage step-up/step-down regulators — for bell voltage, lamp power, ESP32 logic, etc.

  • Cable routing paths — to keep AC and signal wires separated and reduce noise

  • Standoffs or brackets — for securely mounting boards and modules

Labeling and Aesthetics

For clarity and authenticity, the enclosure should include:

  • Silk-screened or engraved labeling for ports and indicators

  • Iconic “Ma Bell” or Bell System-style typography (optional)

  • A matte black or brushed aluminum finish for a professional appearance