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