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

Function of the card:
CTDL-High Speed One Way NPN No Loads
U to T Converter (no loads)

Listed in 1401 SMS card usage

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

Part number: 371590

Used in: IBM 1401, IBM 7070


C: Converter. Used to translate from one voltage level to another, or to change the amplitude of the voltage swing about the same reference level.

References: 2_2 SMS Cards, p31
Coslet data
IBM Standard Modular System, Component Circuits, p160
1_2 SMS Cards, p41
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.