Standard Modular System: Difference between revisions

Revision as of 00:27, 18 March 2018

Revision as of 00:28, 18 March 2018

Line 13:

Some card types could be customized via a "program cap" (a double-rail metal jumper bar with 15 connections) that could be cut to change the circuit configuration. Card types with a "program cap" came with it precut for the standard configuration and if a customer engineer needed a different configuration in the field he could make additional cuts as needed. This feature was intended to reduce the number of different card types a customer engineer had to carry with him to the customer's site.

The card type was a two- to four -letter code embossed on the card (e.g., ''MX, ALQ''). If the card had a "program cap" the code was split into a two letter card type code and a two letter "cap connection" code (e.g., ''AK ZZ'').

When SMS was originally developed, IBM anticipated a set of a couple hundred standard card types would be all that would be needed, making design, manufacture and servicing simpler. Unfortunately that proved far too optimistic as the number of different SMS card types soon grew to well over 2500. Part of the reason for the growth was that multiple [[Digital data|digital]] [[logic families]] were implemented (ECL, RTL, DTL, etc.) as well as [[analog circuit]]s, to meet the requirements of the many different systems the cards were used in.