Bill of Materials

This section lists all components required to assemble the Ma Bell Gateway. Values, part numbers, and notes are included for clarity.

Ref. Des.	Description	Value / Rating	Manufacturer / Part #	Notes
U1	ESP32-WROVER-IE Module	–	Espressif ESP32-WROVER-IE	Main MCU
U2	SLIC, Line Interface IC	HC-5504B (DIP-24)	Intersil / Renesas HC-5504B-5	Subscriber Line Interface Circuit
U3	Audio Codec (if used)	(e.g. ES8311)	[Your preferred part]	PCM/I2S interface between ESP32 & SLIC
J1	RJ11 Jack	6P4C or 6P2C	Amphenol or equivalent	Phone line output
J2	Power Connector	Barrel Jack, 5.5x2.1mm	CUI PJ-102A or equivalent	For 3.3V/9V/-48V supply input
C1, C2, …	Capacitors (see schematic)	[values as needed]	[Mfr/P/N]	Filter, bypass, and timing
R1, R2, …	Resistors (see schematic)	[values as needed]	[Mfr/P/N]	Feed, balance, pull-up/down, etc.
Q1	Relay or MOSFET	–	[Part #]	Ring relay driver or lamp control
D1, D2, …	Diodes/Bridge Rectifier	–	[Part #]	Protection (bridge for line input, etc.)
T1	Transformer (if used for ringing)	20Hz, [spec]	[Part #]	Ring generator
Misc.	PCB, hardware, headers, jumpers	–	–	Enclosure, standoffs, screws, etc.