Four Input Multiplexer Switch A124

This document is a technical schematic for a "Four Input Multiplexer Switch" (part number A124-0-1) produced by Digital Equipment Corporation in 1969. The circuit is designed to switch between four inputs (labeled H, J, L, M, K, N, P) using a series of transistor-based stages (Q1 through Q12) and FETs (Q17 through Q20). The schematic details the arrangement of resistors, capacitors, and diodes (D1 through D15, and D19) required to manage the voltage levels and signal switching, noting that all transistors used are 2N3568 and the diodes are D664.