Manufacturing 1A and 2B ESS Memory - AT&T Archives

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A film made at the Hawthorne Works in Illinois, for Western Electric Hawthorne Works employees, and possibly for system administrators around the country. This black-and-white film was shot with a semi-fisheye lens, and has two parts:
1. How the memory module works (8 minutes)
2. How the memory module is made at Hawthorne Works (12 minutes)
The subject of What a Memory! is the memory modules for the 1A ESS (Electronic Switching System) and 2B ESS. These, as of 1976, were the Bell System's state-of-the-art modules, utilizing electronic reed relays to switch calls. The relays - ferried or remreed switches - consisted of a grid with copper tape loops in one direction, and twisted wire in the other, similar to the magnetic core memory of an early computer. The reed relays were short-lived at Western Electric - semiconductor switching (using integrated circuits) was introduced the following year, in 1977.
The 1A ESS was introduced into service in 1976 in Illinois. It had a capacity of 128,000 phone lines, and was intended for high-traffic urban areas.
The 2B ESS had its first installation in Georgia in February of 1976. This ESS took up seven 18" deep by 26" wide equipment bays, a third of the size of the No. 2 ESS. It could handle 19,000 calls per hour, and then improvements the following year in software and hardware doubled that to 38,000.
Footage Courtesy of AT&T Archives and History Center, Warren, NJ