AT&T 4ESS Tandem List

 

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.

Trailer
Code
(xxx-T)	Location		Type	Install Date	Notes
001	WINDERMERE FL		4ESS	(03/1991)	Verified Jan 2022
002	ALBUQUERQUE 2 NM	4ESS	(11/1977)	
003	ALBANY 3 NY		4ESS	(01/1982)	
004	ANAHEIM 3 CA		4ESS	(03/1981)	Possibly replaced with 158-T?
005	ARLINGTON 3 VA		4ESS	(04/1982)	
006	ATLANTA 5 GA		4ESS	(03/1982)	
007	ATLANTA 4 GA		N4E	Replaced	Verified Jan 2023
008	AUSTIN 2 TX		4ESS	(01/1987)	Verified Jan 2023
009	BUFFALO 2 NY		4ESS	(06/1984)	
010	BALTIMORE 10 MD		4ESS	(08/1980)	Verified Jan 2023
011	BIRMINGHAM 2 AL		4ESS	(04/1981)	
012	BATON ROUGE 2 LA	4ESS	(03/1984)	
013	NEW YORK 5410 NY	4ESS	(07/1991)	
014	CHICAGO 9 IL		4ESS	(08/1987)	
015	CHARLOTTE 3 NC		4ESS	(05/1980)	Verified Jan 2023
016	CHARLESTON 2 WV		4ESS	(02/1982)	Verified Jan 2023
017	CLEVELAND 3 OH		4ESS	(12/1979)	Verified Jan 2023
018	COLUMBIA 2 SC		4ESS	(11/1981)	Verified Jan 2023
019	COLUMBUS 3 OH		N4E	Replaced	Verified Jan 2023
020	COLORADO SPRINGS 2 CO	4ESS	(10/1981)	Verified Jan 2023
021	CAMBRIDGE 19 MA		4ESS	(12/1984)	Verified Jan 2023
022	CAMDEN 3 NJ		4ESS	(04/1979)	(Disconnected late 2022?)
023	CINCINNATI 2 OH		4ESS	(06/1979)	
024	DES MOINES 2 IA		N4E	Replaced	Verified Jan 2023
025	DALLAS 3 TX		4ESS	(12/1976)	Possibly replaced with 154-T?
026	DALLAS 4 TX		4ESS	(04/1981)	Possibly replaced with 154-T?
027	DENVER 5 CO		N4E	Replaced	Verified Jan 2023
028	DETROIT 3 MI		4ESS	(04/1981)	(Disconnected circa 2003?)
029	DAYTON 2 OH		4ESS	(02/1987)	
030	FREEHOLD 2 NJ		N4E     Replaced	Verified Jan 2022
031	FRAMINGHAM 4 MA		4ESS	(05/1987)	Verified Jan 2023
032	FORT WORTH 2 TX		N4E	Replaced	Verified Jan 2023
033	GRAND RAPIDS 3 MI	4ESS	(05/1984)	Verified Jan 2023
034	GREENSBORO 3 NC		N4E	Replaced	Verified Jan 2023 (N4E installed 2022)
035	GARDENA 3 CA		4ESS	(06/1987)	Verified Jan 2023
036	HARRISBURG 2 PA		N/A	Replaced	Disconnected, changed to a 5ESS
037	HOUSTON 4 TX		N4E	Replaced	Verified Jan 2023
038	HOUSTON 5 TX		4ESS	(07/1988)	
039	INDIANAPOLIS 2 IN	4ESS	(10/1980)	
040	JACKSON 2 MS		4ESS	(04/1983)	
041	JACKSONVILLE 3 FL	4ESS	(12/1976)	
042	KNOXVILLE 2 TN		4ESS	(12/1980)	Verified Jan 2023
043	KANSAS CITY 2 MO	N4E	Replaced	Verified Jan 2023
044	LANSING 3 MI		4ESS	(05/1987)	Verified Jan 2023
045	LOS ANGELES 5 CA	4ESS	(02/1983)	(Was this replaced with a N4E?)
046	LOS ANGELES 6 CA	4ESS	(04/1988)	(Was this replaced with a N4E?)
047	LOUISVILLE 2 KY		4ESS	(07/1980)	Verified Jan 2023
048	LITTLE ROCK 2 AR	N4E	Replaced	Verified Jan 2023
049	MACON 3 GA		4ESS	(04/1987)	Verified Jan 2023
050	MIDLAND 2 TX		4ESS	(10/1983)	Verified Jan 2023
051	MEMPHIS 2 TN		4ESS	(02/1981)	(Disconnected late 2022?)
052	MANCHESTER 3 NH		4ESS	(04/1982)	(Disconnected late 2022?)
053	(presently unassigned)	N/A	N/A	        N/A
054	MINNEAPOLIS 3 MN	4ESS	(05/1980)	Verified Jan 2023
055	MINNEAPOLIS 4 MN	4ESS	(06/1988)	
056	MONTGOMERY 2 AL		N4E	Replaced        Verified Jan 2023
057	NORFOLK 4 VA		4ESS	(04/1981)	
058	NASHVILLE 2 TN		N4E	Replaced	Verified Jan 2023
059	NEW HAVEN 5 CT		4ESS	(10/1981)	Verified Jan 2023
060	NEW ORLEANS 3 LA	4ESS	(06/1980)	
061	NEWARK 8 NJ		4ESS	(06/1980)	Verified Jan 2023
062	NEW YORK 24 NY		4ESS	(04/1978)	
063	NEW YORK 51 NY		4ESS	(11/1984)	
064	NEW YORK 5450 NY	4ESS	(01/1981)	
065	NEW YORK 12 NY(QUEENS)	N4E	Replaced	Verified Jan 2023
066	OJUS 3 FL		4ESS	(05/1978)	
067	OAKBROOK 2 IL		4ESS	(03/1981)	(Disconnected late 2022?)
068	OAKBROOK 3 IL		4ESS	(06/1988)	Verified Jan 2023
069	OKLAHOMA CITY 2 OK	4ESS	(05/1979)	(Disconnected late 2022?)
070	OAKLAND 6 CA		N4E	Replaced	Verified Jan 2023 (N4E installed in 2022)
071	OMAHA 2 NE		N4E	Replaced	Verified Jan 2023
072	ORLANDO 3 FL		4ESS	(09/1980)	
073	PEORIA 3 IL		4ESS	(02/1983)	Verified Jan 2023
074	PHILADELPHIA 4 PA	4ESS	(05/1980)	(Disconnected late 2022?)
075	PHOENIX 3 AZ		4ESS	(09/1980)	
076	PITTSBURGH 3 PA		N4E	Replaced	Verified Jan 2023 (N4E installed in 2021)
077	PORTLAND 3 OR		4ESS	(04/1979)	
078	RICHMOND 2 VA		4ESS	(05/1979)	
079	ROCKY MOUNT 3 NC	4ESS	(06/1982)	
080	ROCHELLE PARK 3 NJ	4ESS	(08/1982)	
081	RENO 4 NV		4ESS	(05/1982)	Verified Jan 2023
082	SOUTH BEND 3 IN		4ESS	(04/1987)	Verified Jan 2023
083	SACRAMENTO 4 CA		N4E	Replaced	Verified Jan 2023
084	SHERMAN OAKS 5 CA	N4E	Replaced	Verified Jan 2023
085	STOCKTON 3 CA		4ESS	(03/1984)	Verified Jan 2023
086	SALT LAKE CITY 2 UT	4ESS	(04/1982)	Verified Jan 2023
087	SAN ANTONIO 2 TX	4ESS	(05/1977)	
088	SAN DIEGO 3 CA		N4E	Replaced	Verified Jan 2023
089	SAN FRANCISCO 4 CA	N4E	Replaced	Verified Jan 2023
090	SAN JOSE 3 CA		4ESS	(03/1982)	Verified Jan 2023
091	SPRINGFIELD 2 IL	4ESS	(04/1985)	Verified Jan 2023
092	SPRINGFIELD 3 MA	4ESS	(05/1980)	Verified Jan 2023
093	SPOKANE 2 WA		4ESS	(10/1982)	(Disconnected late 2022?)
094	SAINT LOUIS 3 MO	N4E	Replaced	Verified Jan 2023
095	SEATTLE 4 WA		4ESS	(05/1980)	(Disconnected late 2022?)
096	SYRACUSE 2 NY		4ESS	(03/1985)	Verified Jan 2023
097	TAMPA FL		4ESS	(11/1986)	
098	TOLEDO 2 OH		4ESS	(04/1984)	Verified Jan 2023
099	TULSA 2 OK		4ESS	(06/1980)	
100	WASHINGTON 6 DC		4ESS	(03/1978)	
101	WAYNE 2 PA		4ESS	(09/1977)	Possibly replaced?
102	WICHITA 2 KS		4ESS	(04/1981)	
103	WHITE PLAINS 3 NY	N4E	Replaced	Verified Jan 2023 (N4E installed in 2022)
104	WHITE PLAINS 5 NY	4ESS	(08/1980)	May have been replaced with 103-T
105	WAUKESHA 3 WI		N4E	(03/1979)	Verified Jan 2023 (N4E installed in 2022)
106	WEST PALM BEACH 4 FL	4ESS	(08/1981)	
107	AKRON 4 OH		4ESS	(04/1989)	Verified Oct 2022
108	ATLANTA 7 GA		4ESS	(11/1988)	
109	BLOOMINGTON 2 IN	4ESS	(11/1989)	
110	CHICAGO 11 IL		4ESS	(01/1990)	
111	NEW YORK 55 NY		N4ES	Replaced	Verified Jan 2023
112	PLYMOUTH 2 MI		4ESS	(12/1989)	
113	SAN BERNARDINO 2 CA	4ESS	(03/1989)	Verified Jan 2023
114	TUCSON 3 AZ		4ESS	(10/1989)	Verified Jan 2023
115	PITTSBURGH 9 PA		4ESS	(12/1988)	Verified Jan 2023
116	OMAHA 3 NE		4ESS	(07/1990)	
117	HAMILTON SQUARE 2 NJ	4ESS	(07/1991)	Verified Jan 2023
118	WORCESTER 3 MA		4ESS	(12/1991)	
119	CHESHIRE CT		4ESS	(01/1992)	Verified Jan 2023
120	NEW YORK 25 NY		4ESS	(02/1992)	
121	HILLSBORO MO		4ESS	(05/1992)	Verified Jan 2023
122	FINKSBURG MD		N4E	Replaced	Verified Jan 2023 (does not ID with an NSN)
123	ADAMS TX		4ESS	(10/1992)	Verified Jan 2023
124	PLANO IL		4ESS	(12/1992)	(standby tandem?)
125	ELLISVILLE FL		4ESS	(10/1992)	Verified Jan 2023
126	MONTICELLO 2 GA		4ESS	(10/1992)	Verified Jan 2023
127	CEDAR KNOLLS 2 NJ	4ESS	(10/1992)	Verified Oct 2022
128	TACOMA 2 WA		4ESS	(12/1992)	
129	DUNNIGAN CA		N4E	Replaced	Verified Jan 2023 (male voice on ID)
130	GARDENA 4 CA		4ESS	(04/1993)	Possibly replaced with 152-T?
131	FORT LAUDERDALE FL	4ESS	(05/1993)	Verified Jan 2023
132	MADISON 3 WI		4ESS	(11/1992)	Verified Jan 2023
133	WHITE PLAINS 4 NY	4ESS	(08/1993)	
134	MARKHAM ON    (905-U2)	4ESS	(06/1993)	Possibly retired
135	CHERRYVILLE NJ		4ESS	(05/1993)	
136	CAMBRIDGE MA		4ESS	(06/1993)	
137	ALDERGROVE BC (604-U2)	4ESS	(08/1993)	Possibly retired
138	OXNARD CA		4ESS	(07/1993)	
139	ANCHORAGE AK		4ESS	(03/1996)	Verified Jan 2023
140	MESA AZ		4ESS 2nd Gen	(1998/1999)	
141	DURHAM NC	4ESS 2nd Gen	(1998/1999)	Verified Jan 2023
142	DENVER 6 CO	4ESS 2nd Gen	(1998/1999)	
143	FORT MYERS FL	4ESS 2nd Gen	(1998/1999)	Possibly replaced
144	MONROVIA MD	4ESS 2nd Gen	(1998/1999)	Verified Feb 2023
145	CHICAGO IL	4ESS 2nd Gen	(1998/1999)	
146	ATLANTA GA 	4ESS 2nd Gen	(07/1999)	Last traditional #4ESS
147	CHICAGO IL (?)		N4E	2012?	        Verified Feb 2023
148	BOSTON MA (?)		N4E	?	        
149	MESA AZ (?)		N4E	?	        Verified Jan 2023
150	ATLANTA GA (?)		N4E	?	
151	FORT MYERS FL (?)	N4E	?	        Verified Jan 2023
152	GARDENA CA (?)		N4E	(08/2013)	Verified Jan 2023
153	??? MA (?)		N4E	?	        Verified Jan 2023
154	DALLAS TX (?)		N4E	?	        Verified Jan 2023
155	SCOTTSDALE AZ (?)	N4E	?	        Verified Jan 2023
156	SYRACUSE NY (?)		N4E	?	        Verified Jan 2023
157	JACKSONVILLE FL (?)	N4E	?	        Verified Jan 2023
158	ANAHEIM CA (?)		N4E	?	        Verified Jan 2023
159	WAYNE PA (?)		N4E	2016?	        Verified Jan 2023