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

Function of the card:
Ctrl-inverter "n" 2 way
Ctrl - inverter n 2 way
Ctrl-inverter 4 2 way
CTRL-Inverter "N" 2 Way Extender
CTRL Inverter "N" 2 Way
Crtl - inverter "n" 2 way

Listed in 1401 SMS card usage
Quad 2 Input Open Collector NAND

Complemented Transistor Resistor Logic (CTRL) is IBM's term for a form of resistor-transistor logic.

Part number: 371661

PCB number: 492867

Used in: IBM 1620, IBM 1410, IBM 729V, IBM 1311 Disk, IBM 1414 I/O Synchronizer, 7040, 1622, 1626

Symbol:O, E, A, O

IBM SMS card type MX 371661 IBM SMS card type MX 371661 IBM SMS card type MX 371661 IBM SMS card type MX 371661

Image courtesy of Henk Stegeman
Image courtesy of Roberto Gonzalez Rocha


A I2
B I1
C O3
D I1
E I3
F I3
G O1
H I2
K O4
M -12V
N +12VM
Q I4
R I4
References: 1410_SMS_VOL_2.pdf, p104
Coslet data
IBM 1311 ILD, p134
1626 Plotter Parts
IBM 1620 Instructional System Diagrams, p485
National Museum of Computing.
IBM 1620 FE Catalog

This page created by Ken Shirriff on Wed Sep 15 18:15:09 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.