The following continuing on maintaining an active list of AT&T Class 4 Tandems. All of the original Number 4 Electronic Switching System (#4ESS) Class 4 Tandems were finally turned off in early 2026. This is the successor list of the Class 4 Tandems remaining in the AT&T long distance network.
Though the #4ESS switch was first installed in 1976, the first N4E tandem started arriving circa 2012. This is the successor switch called the Next Generation 4ESS or N4E. The N4E emulates the #4ESS software in a new hardware environment. The main difference to the end user is that the tandem recordings are very clean (no magnetic drums) and sound a bit robotic in nature.
This list ONLY contains the active N4E tandems in the network. If you’re looking for the original 4ESS tandems – click on the Classic 4ESS Tandem List (1976-2026).
In many cases, the new N4E tandems replaced existing 4ESS tandems and took their Network Switch Number (NSN), while in other cases they were brand new to the network (those numbering 147 and higher). It is assumed that some of these N4Es replaced some #5ESS “edge tandems” in the AT&T network and upgraded them to full Class 4 tandems.
The locations for the new N4E switches (147 and higher) are best guesses. The other ones (146 and lower) took on the identity of the #4ESS that they replaced.
The last #4ESS in Anchorage, AK left the network in early 2026. As of March 2026 there are approximately 45 N4E tandems in the network.
Confirmed 4ESS or N4E - Survey as of March 2026 NSN Switch Name, ST Type Last Verified Date 007 ATLANTA 4 GA N4E Mar 2026 019 COLUMBUS 3 OH N4E Mar 2026 024 DES MOINES 2 IA N4E Mar 2026 027 DENVER 5 CO N4E Mar 2026 030 FREEHOLD 2 NJ N4E Mar 2026 032 FORT WORTH 2 TX N4E Mar 2026 034 GREENSBORO 3 NC N4E Mar 2026 037 HOUSTON 4 TX N4E Mar 2026 040 JACKSON 2 MS N4E Mar 2026 043 KANSAS CITY 2 MO N4E Mar 2026 048 LITTLE ROCK 2 AR N4E Mar 2026 058 NASHVILLE 2 TN N4E Mar 2026 065 NEW YORK 12 NY(QUEENS) N4E Mar 2026 070 OAKLAND 6 CA N4E Mar 2026 071 OMAHA 2 NE N4E Mar 2026 076 PITTSBURGH 3 PA N4E Mar 2026 077 PORTLAND 3 OR N4E Mar 2026 078 RICHMOND 2 VA N4E Mar 2026 083 SACRAMENTO 4 CA N4E Mar 2026 084 SHERMAN OAKS 5 CA N4E Mar 2026 087 SAN ANTONIO 2 TX N4E Mar 2026 088 SAN DIEGO 3 CA N4E Mar 2026 089 SAN FRANCISCO 4 CA N4E Mar 2026 094 SAINT LOUIS 3 MO N4E Mar 2026 100 WASHINGTON 6 DC N4E Mar 2026 103 WHITE PLAINS 3 NY N4E Mar 2026 105 WAUKESHA 3 WI N4E Mar 2026 110 CHICAGO 11 IL N4E Mar 2026 111 NEW YORK 55 NY N4E Mar 2026 147 Chicago IL? N4E Oct 2025 148 Boston MA? N4E Oct 2025 149 Mesa AZ? N4E Mar 2026 150 Atlanta GA? N4E Oct 2025 151 Fort Myers, FL? N4E Mar 2026 152 Gardena CA? N4E Mar 2026 153 MA? N4E Mar 2026 154 Dallas TX? N4E Mar 2026 155 Scottsdale AZ? N4E Mar 2026 156 Buffalo? N4E Mar 2026 157 Jacksonville FL? N4E Mar 2026 158 Anaheim, CA? N4E Mar 2026 159 Wayne PA? N4E Mar 2026 Possibly still in service, but not 100% sure NSN Switch Name, ST Type Last Verified Date 056 MONTGOMERY 2 AL N4E Oct 2025 129 DUNNIGAN CA N4E May 2023
Looking for the old 4ESS tandem list? It’s now been relocated to the Classic 4ESS Tandem List (1976-2026)