R121

This document is an electrical schematic titled "NAND GATE R121" (Document Number CS R121-0-1, Revision A) from Digital Equipment Corporation, copyrighted 1965.

The schematic illustrates a circuit primarily composed of four transistors (Q1-Q4, specified as DEC 3639B / EIA 2N3639), numerous diodes (types D-662 / EIA IN645 and D-664 / EIA IN3606), and various resistors (1/4 W, 5% tolerance). It features multiple input lines (S, T, U, V, M, N, O, P, J, K, E, F) and several output points (OD, OH, OL, ON). The circuit requires power supplies of +10V, Ground, -15V, and a -3V "STRATE" supply.

The document includes a "Transistor & Diode Conversion Chart" and notes that the schematic is proprietary, intended solely for test and maintenance purposes.