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

Function of the card:
SDTDL data reg. and inhbt driver
Inhibit circuit
SDTDL Data Register and Inhibit Driver

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

Part number: 372220

Customer Eng reference number: 734392

Used in: IBM 1443 Printer, IBM 2821 Control Unit

IBM SMS card type YKR 372220 IBM SMS card type YKR 372220

References: IBM 1443 ALD, p118
IBM 2821 CCD, p94
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.