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

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

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

Cap code: None (details)

Symbol: DI

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

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

The information on these pages comes from a variety of sources, especially old IBM documents on bitsavers.org, 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.