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

Function of the card:
Ctdl extender card field replacement

Complemented Transistor Diode Logic (CTDL) is IBM's term for a form of diode-transistor logic.

Part number: 370979

Field replacement part number: 370979

PCB number: 526999

Used in: IBM 1401

IBM SMS card type CL 370979 IBM SMS card type CL 370979

Image courtesy of Henk Stegeman

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.