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

Function of the card:
Alloy-indicator driver 15 ma
CTDL Low Current Indicator Driver

Germanium alloy transistors were an early type of transistor, faster than the earlier grown-junction transistors.

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

Part number: 371528

Used in: IBM 1410, 7030, IBM 7070


DI: Driver, Indicator. Driver operating into an indicating device.

References: IBM Standard Modular System, Component Circuits, p132
1410_SMS_VOL_2.pdf, p87
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.