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

Function of the card:
SDTDL single shot

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

Part number: 372275

Customer Eng reference number: 734405

PCB number: 399551

Used in: IBM 2821 Control Unit


SS: Single Shot. Provides a monostable output which can be pulsed into its quasi-stable state for a predetermined duration. with each input triggering pulse or triggering voltage change. Once triggered, the output pulse duration becomes independent of input time duration or amplitude.
IBM SMS card type AZK 372275 IBM SMS card type AZK 372275

Image courtesy of Richard Stuve

References: IBM 2821 CCD, p36
This page created by Ken Shirriff on Wed Sep 15 18:15:10 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.