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 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 Jun 2022 008 AUSTIN 2 TX 4ESS (01/1987) Verified May 2022 009 BUFFALO 2 NY 4ESS (06/1984) 010 BALTIMORE 10 MD 4ESS (08/1980) Verified Apr 2022 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 Apr 2022 016 CHARLESTON 2 WV 4ESS (02/1982) Verified May 2022 017 CLEVELAND 3 OH 4ESS (12/1979) Verified Apr 2022 018 COLUMBIA 2 SC 4ESS (11/1981) Verified Jun 2022 019 COLUMBUS 3 OH N4E Replaced Verified Jun 2022 020 COLORADO SPRINGS 2 CO 4ESS (10/1981) Verified May 2022 021 CAMBRIDGE 19 MA 4ESS (12/1984) 022 CAMDEN 3 NJ 4ESS (04/1979) Verified Jun 2022 023 CINCINNATI 2 OH 4ESS (06/1979) 024 DES MOINES 2 IA N4E Replaced Verified Apr 2022 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 May 2022 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 May 2022 032 FORT WORTH 2 TX N4E Replaced Verified Jun 2022 033 GRAND RAPIDS 3 MI 4ESS (05/1984) Verified Jun 2022 034 GREENSBORO 3 NC N4E Replaced Verified Jun 2022 035 GARDENA 3 CA 4ESS (06/1987) Verified Jun 2022 036 HARRISBURG 2 PA N/A Replaced Changed to a 5ESS 037 HOUSTON 4 TX N4E Replaced Verified May 2022 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 May 2022 043 KANSAS CITY 2 MO N4E Replaced Verified Jun 2022 044 LANSING 3 MI 4ESS (05/1987) Verified May 2022 045 LOS ANGELES 5 CA 4ESS (02/1983) 046 LOS ANGELES 6 CA 4ESS (04/1988) 047 LOUISVILLE 2 KY 4ESS (07/1980) Verified May 2022 048 LITTLE ROCK 2 AR N4E Replaced Verified May 2022 049 MACON 3 GA 4ESS (04/1987) Verified May 2022 050 MIDLAND 2 TX 4ESS (10/1983) Verified Jun 2022 051 MEMPHIS 2 TN 4ESS (02/1981) Verified Jun 2022 052 MANCHESTER 3 NH 4ESS (04/1982) Verified May 2022 053 (presently unassigned) N/A N/A N/A 054 MINNEAPOLIS 3 MN 4ESS (05/1980) Verified Jun 2022 055 MINNEAPOLIS 4 MN 4ESS (06/1988) 056 MONTGOMERY 2 AL N4E Replaced Verified Jan 2022 057 NORFOLK 4 VA 4ESS (04/1981) 058 NASHVILLE 2 TN N4E Replaced Verified May 2022 059 NEW HAVEN 5 CT 4ESS (10/1981) Verified Jun 2022 060 NEW ORLEANS 3 LA 4ESS (06/1980) 061 NEWARK 8 NJ 4ESS (06/1980) Verified Apr 2022 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 May 2022 066 OJUS 3 FL 4ESS (05/1978) 067 OAKBROOK 2 IL 4ESS (03/1981) 068 OAKBROOK 3 IL 4ESS (06/1988) 069 OKLAHOMA CITY 2 OK 4ESS (05/1979) 070 OAKLAND 6 CA 4ESS (08/1981) 071 OMAHA 2 NE N4E Replaced Verified Jun 2022 072 ORLANDO 3 FL 4ESS (09/1980) 073 PEORIA 3 IL 4ESS (02/1983) Verified May 2022 074 PHILADELPHIA 4 PA 4ESS (05/1980) Verified May 2022 075 PHOENIX 3 AZ 4ESS (09/1980) 076 PITTSBURGH 3 PA N4E Replaced Verified Apr 2022 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 Apr 2022 082 SOUTH BEND 3 IN 4ESS (04/1987) Verified May 2022 083 SACRAMENTO 4 CA N4E Replaced Verified Jun 2022 084 SHERMAN OAKS 5 CA N4E Replaced Verified Jun 2022 085 STOCKTON 3 CA 4ESS (03/1984) Verified Apr 2022 086 SALT LAKE CITY 2 UT 4ESS (04/1982) Verified Jun 2022 087 SAN ANTONIO 2 TX 4ESS (05/1977) 088 SAN DIEGO 3 CA N4E Replaced Verified Jun 2022 089 SAN FRANCISCO 4 CA N4E Replaced Verified May 2022 090 SAN JOSE 3 CA 4ESS (03/1982) Verified May 2022 091 SPRINGFIELD 2 IL 4ESS (04/1985) Verified Apr 2022 092 SPRINGFIELD 3 MA 4ESS (05/1980) Verified May 2022 093 SPOKANE 2 WA 4ESS (10/1982) Verified May 2022 094 SAINT LOUIS 3 MO N4E Replaced Verified May 2022 095 SEATTLE 4 WA 4ESS (05/1980) Verified Jun 2022 096 SYRACUSE 2 NY 4ESS (03/1985) Verified May 2022 097 TAMPA FL 4ESS (11/1986) 098 TOLEDO 2 OH 4ESS (04/1984) Verified Jun 2022 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 4ESS (01/1987) 104 WHITE PLAINS 5 NY 4ESS (08/1980) Verified Jun 2022 105 WAUKESHA 3 WI 4ESS (03/1979) 106 WEST PALM BEACH 4 FL 4ESS (08/1981) 107 AKRON 4 OH 4ESS (04/1989) 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 May 2022 112 PLYMOUTH 2 MI 4ESS (12/1989) 113 SAN BERNARDINO 2 CA 4ESS (03/1989) Verified Jun 2022 114 TUCSON 3 AZ 4ESS (10/1989) Verified May 2022 115 PITTSBURGH 9 PA 4ESS (12/1988) 116 OMAHA 3 NE 4ESS (07/1990) 117 HAMILTON SQUARE 2 NJ 4ESS (07/1991) 118 WORCESTER 3 MA 4ESS (12/1991) 119 CHESHIRE CT 4ESS (01/1992) Verified Apr 2022 120 NEW YORK 25 NY 4ESS (02/1992) 121 HILLSBORO MO 4ESS (05/1992) 122 FINKSBURG MD 4ESS (07/1992) 123 ADAMS TX 4ESS (10/1992) Verified May 2022 124 PLANO IL 4ESS (12/1992) (standby tandem) 125 ELLISVILLE FL 4ESS (10/1992) 126 MONTICELLO 2 GA 4ESS (10/1992) Verified May 2022 127 CEDAR KNOLLS 2 NJ 4ESS (10/1992) 128 TACOMA 2 WA 4ESS (12/1992) 129 DUNNIGAN CA N4E Replaced Verified Apr 2022 130 GARDENA 4 CA 4ESS (04/1993) Possibly replaced with 152-T? 131 FORT LAUDERDALE FL 4ESS (05/1993) Verified May 2022 132 MADISON 3 WI 4ESS (11/1992) Verified Jun 2022 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 Jun 2022 140 MESA AZ 4ESS 2nd Gen (1998/1999) 141 DURHAM NC 4ESS 2nd Gen (1998/1999) Verified Jan 2022 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 Jun 2022 145 CHICAGO IL 4ESS 2nd Gen (1998/1999) 146 ATLANTA GA 4ESS 2nd Gen (07/1999) Last traditional #4ESS 147 CHICAGO IL (?) N4E 2012? 148 BOSTON MA (?) N4E ? 149 MESA AZ (?) N4E ? Verified May 2022 150 ATLANTA GA (?) N4E ? 151 FORT MYERS FL (?) N4E ? Verified May 2022 152 GARDENA CA (?) N4E (08/2013) Verified Apr 2022 153 ??? MA (?) N4E ? Verified Jun 2022 154 DALLAS TX (?) N4E ? Verified May 2022 155 SCOTTSDALE AZ (?) N4E ? Verified May 2022 156 SYRACUSE NY (?) N4E ? Verified May 2022 157 JACKSONVILLE FL (?) N4E ? Verified Jun 2022 158 ANAHEIM CA (?) N4E ? Verified May 2022 159 WAYNE PA (?) N4E 2016? Verified Jun 2022