The following is a work in progress in trying to maintain an active catalog of the Number 4 Electronic Switching System (#4ESS) Class 4 Tandem list for the AT&T long distance network. This list is a successor to the original list made by the late telephone historian and researcher Mark Cuccia (1961-2014) to try to encompass the changes in the #4ESS network since his passing.
The #4ESS switch was first installed in Chicago, IL in 1976 as the successor to the 4A crossbar switch. Over 100 #4ESS switches were installed in the PSTN by the early 1990s for AT&T Long Lines, and a number of them were also used for the regional Bell operating companies. A second batch of #4ESS switches (what I call “2nd Generation”) were installed in 1998-1999 and were the last #4ESS switches installed in the PSTN, with the one in Atlanta (number 146-T) being the last one ever.
Starting in or around 2012, a new batch of #4ESS type Class 4 switches were starting to show up in the PTSN. 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 not only contains the #4ESSes in the network, but the new N4E switches as well. In some cases, there are N4E switches that are replacing 4ESS switches, and in some cases they are brand new to the network (those numbering 147 and higher). It is assumed that the new N4Es are replacing the #5ESS switches that were originally installed to be “edge tandems” in the AT&T network and upgrading them to full Class 4 tandems.
The locations for the new N4E switches are best guesses, and in some cases appears to be replacing existing #4ESS switches and taking on new identities, while in other cases they take on the old trailer code (known as the Network Switch Number of NSN) of the #4ESS that they replaced.
NSN Switch Name, ST Type Install Date Last Verified Date 001 WINDERMERE FL 4ESS 03/01/91 Jan 2022 007 ATLANTA 4 GA N4E Replaced Mar 2024 008 AUSTIN 2 TX 4ESS 01/01/87 Mar 2024 010 BALTIMORE 10 MD 4ESS 08/01/80 Mar 2024 011 BIRMINGHAM 2 AL 4ESS 04/01/81 Mar 2024 012 BATON ROUGE 2 LA 4ESS 03/01/84 Nov 2023 014 CHICAGO 9 IL 4ESS 08/01/87 Jan 2022 019 COLUMBUS 3 OH N4E Replaced Mar 2024 020 COLORADO SPRINGS 2 CO 4ESS 10/01/81 Mar 2024 021 CAMBRIDGE 19 MA 4ESS 12/01/84 Jan 2023 024 DES MOINES 2 IA N4E Replaced Mar 2024 027 DENVER 5 CO N4E Replaced Nov 2023 030 FREEHOLD 2 NJ N4E Replaced Mar 2024 031 FRAMINGHAM 4 MA 4ESS 05/01/87 Mar 2024 032 FORT WORTH 2 TX N4E Replaced Mar 2024 033 GRAND RAPIDS 3 MI 4ESS 05/01/84 Mar 2024 034 GREENSBORO 3 NC N4E Replaced Mar 2024 035 GARDENA 3 CA 4ESS 06/01/87 Mar 2024 037 HOUSTON 4 TX N4E Replaced Mar 2024 040 JACKSON 2 MS N4E Replaced Mar 2024 043 KANSAS CITY 2 MO N4E Replaced Mar 2024 044 LANSING 3 MI 4ESS 05/01/87 Mar 2024 047 LOUISVILLE 2 KY 4ESS 07/01/80 Mar 2024 048 LITTLE ROCK 2 AR N4E Replaced Mar 2024 049 MACON 3 GA 4ESS 04/01/87 Mar 2024 052 MANCHESTER 3 NH N4E Replaced May 2022 056 MONTGOMERY 2 AL N4E Replaced Jun 2022 058 NASHVILLE 2 TN N4E Replaced Mar 2024 065 NEW YORK 12 NY(QUEENS) N4E Replaced Mar 2024 067 OAKBROOK 2 IL N4E Replaced Mar 2024 068 OAKBROOK 3 IL 4ESS 06/01/88 Mar 2024 070 OAKLAND 6 CA N4E Replaced Mar 2024 071 OMAHA 2 NE N4E Replaced Mar 2024 073 PEORIA 3 IL 4ESS 02/01/83 11/4/2023 074 PHILADELPHIA 4 PA 4ESS 05/01/80 Mar 2024 076 PITTSBURGH 3 PA N4E Replaced Mar 2024 077 PORTLAND 3 OR N4E Replaced Mar 2024 078 RICHMOND 2 VA N4E Replaced Mar 2024 082 SOUTH BEND 3 IN 4ESS 04/01/87 Mar 2024 083 SACRAMENTO 4 CA N4E Replaced Mar 2024 084 SHERMAN OAKS 5 CA N4E Replaced Mar 2024 085 STOCKTON 3 CA 4ESS 03/01/84 Mar 2024 086 SALT LAKE CITY 2 UT 4ESS 04/01/82 Mar 2024 087 SAN ANTONIO 2 TX N4E Replaced Nov 2023 088 SAN DIEGO 3 CA N4E Replaced Jan 2023 089 SAN FRANCISCO 4 CA N4E Replaced Nov 2023 091 SPRINGFIELD 2 IL 4ESS 04/01/85 Mar 2024 094 SAINT LOUIS 3 MO N4E Replaced Mar 2024 096 SYRACUSE 2 NY 4ESS 03/01/85 Mar 2024 098 TOLEDO 2 OH 4ESS 04/01/84 Mar 2024 100 WASHINGTON 6 DC N4E Replaced Nov 2023 103 WHITE PLAINS 3 NY N4E Replaced Mar 2024 105 WAUKESHA 3 WI N4E Replaced Feb 2023 107 AKRON 4 OH 4ESS 04/01/89 Oct 2022 110 CHICAGO 11 IL N4E Replaced Mar 2024 111 NEW YORK 55 NY N4E Replaced Mar 2024 114 TUCSON 3 AZ 4ESS 10/01/89 Mar 2024 115 PITTSBURGH 9 PA 4ESS 12/01/88 Jun 2023 117 HAMILTON SQUARE 2 NJ 4ESS 07/01/91 Jan 2023 121 HILLSBORO MO 4ESS Unknown Jan 2023 122 FINKSBURG MD N4E Replaced Mar 2024 124 PLANO IL 4ESS 12/01/92 Mar 2024 125 ELLISVILLE FL 4ESS 10/01/92 May 2023 126 MONTICELLO 2 GA 4ESS 10/01/92 Mar 2024 127 CEDAR KNOLLS 2 NJ 4ESS 10/01/92 Oct 2022 129 DUNNIGAN CA N4E Replaced May 2023 132 MADISON 3 WI 4ESS 11/01/92 Mar 2024 139 ANCHORAGE AK 4ESS 03/01/96 Mar 2024 141 DURHAM NC 4ESS 1998/1999 Nov 2023 144 MONROVIA MD 4ESS 1998/1999 Nov 2023 147 Chicago IL? N4E 2012? Jan 2023 148 Boston MA? N4E ? Mar 2024 149 Mesa AZ? N4E ? Mar 2024 150 Atlanta GA? N4E ? Aug 2023 151 Fort Myers, FL? N4E ? Mar 2024 152 Gardena CA? N4E 2012? Mar 2024 153 MA? N4E ? Mar 2024 154 Dallas TX? N4E ? Mar 2024 155 Scottsdale AZ? N4E ? Mar 2024 156 Buffalo? N4E ? Mar 2024 157 Jacksonville FL? N4E ? Mar 2024 158 Anaheim, CA? N4E ? Mar 2024 159 Wayne PA? N4E 2016? Mar 2024