 The 1AESS tape drives had approximately four times the density of the original ones in 1ESS, and were used for some of the same purposes as in other mainframe computers, including program updates and loading special programs.Most of the thousands of 1ESS and 1AESS offices in the USA were replaced in the 1990s by DMS-100, 5ESS Switch and other digital switches, and since 2010 also by packet switches.As of late 2014, just over 20 1AESS installations remained in the North American network, which were located mostly in AT&T's legacy BellSouth and AT&T's legacy Southwestern Bell states, especially in the Atlanta GA metro area, the Saint Louis MO metro area, and in the Dallas/Fort Worth TX metro area.