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