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

Function of the card:
Current Mode to CTDL Power Inverter

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

Part number: 371541

Used in: IBM 7070


IP: Inverter, Power. Performs function of an inverter white also driving a line.

References: IBM Standard Modular System, Component Circuits, p146
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.