M5940

This document is a schematic diagram for a Digital Equipment Corporation (DEC) EIA Level Converter, identified by part number M5940-0-1.

The converter's primary function is to translate EIA standard input signals into EIA standard output signals using a series of logic gates.

Key features and components include:

• EIA Inputs: Signals enter through a series of buffers/inverters (primarily using DEC1489 ICs, designated E3 and E6) with 470pF capacitors for signal conditioning.

• Logic Gates: The conversion involves three types of integrated circuits:

  • DEC1489 (E3, E6): Used for initial input buffering.
  • DEC7404 (E1, E2, E5): Likely performing intermediate logic or buffering.
  • DEC1488 (E4, E7): Responsible for driving the EIA output signals.

• EIA Outputs: Signals exit from the DEC1488 gates (E4, E7), each typically with a 330pF capacitor to ground.

• Power Supply: The circuit requires multiple voltage rails, including +15V, +11V, -11V, -15V, and +5V. Specific notes indicate +5V and Ground connections for the ICs. Diodes (D672, 1N746A 3.3V Zener) and resistors (1.5K) are part of the power distribution and protection.
• Capacitors: A variety of capacitors (470pF, 330pF, 0.01uF, 0.39uF) are used throughout for filtering, decoupling, and signal conditioning.
• Parts List: A detailed list of all components, including their quantities, descriptions, and DEC part numbers, is provided.

The document also includes copyright information (1971 by Digital Equipment Corporation) and revision history.