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

Function of the card:
SDTDL double level logic block #2a low speed, wo loads
SDTDL-Double Level Logic Block #2A Low Speed, wo Loads

Listed in 1401 SMS card usage

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

Part number: 370358

PCB number: 484135

Used in: IBM 1401, IBM 1410

References: 2_2 SMS Cards, pp103,104
1410_SMS_VOL_1.pdf, p92
Coslet data
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.