IBM Standard Modular System

The Standard Modular System (SMS) was a system of standard transistorized circuit boards and mounting racks developed by IBM in the late 1950s, originally for the IBM 7030 Stretch. They were used throughout IBM's second generation computers, peripherals, the 7000 series, the 1400 series, and the 1620. SMS was superseded by Solid Logic Technology (SLT) introduced with System/360 in 1964, however they remained in use with legacy systems through the 1970s.