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

Function of the card:
SDTDL low speed trigger
Trigger ls

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

Trigger is IBM's term for a flip flop or latch.

Part number: 372239

Customer Eng reference number: 734347

PCB number: 484991 , hole pattern: 493457

Used in: IBM 1443 Printer, IBM 2821 Control Unit

Symbol:E, T

E: Extender. Provides additional inputs to logical blocks and triggers. Adds to drivers the ability to drive more loads.

T: Trigger. A conditioned bi-stable device whose steady-state outputs change from one stable state to the other with two separate triggering levels, pulses, or voltage changes. The set input turns the trigger on if the reset input Is not on, and vice versa.

References: IBM 2821 CCD, p35
IBM 1443 ALD, p88
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.