This page describes the IBM SMS card "DHU", and is part of the SMS card database.

Function of the card:
SDTDL-H.S. Logic Inverter W/O Load
SDTDL-h.s. logic inverter wo/l

Saturated Drift Transistor Diode Logic (SDTDL) is a form of Diode-transistor logic using faster drift-field transistors.

Part number: 372169

PCB number: 399591

Used in: IBM 1311 Disk

References: IBM 1311 ILD, p128
Coslet data
National Museum of Computing.
This page created by Ken Shirriff on Wed Sep 15 18:15:11 2021.

The information on these pages comes from a variety of sources, especially old IBM documents on, as well as information from the IBM 1401 restoration team, especially Tim Coslet's SMS data and Jim Hunt's data. Much of this information was obtained through OCR, so don't expect complete accuracy. These pages are not associated with IBM in any way.