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) Possibly retired? 002 ALBUQUERQUE 2 NM 4ESS (11/1977) Mexican gateway 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 Caribbean gateway 008 AUSTIN 2 TX 4ESS (01/1987) 009 BUFFALO 2 NY 4ESS (06/1984) Canadian Gateway 010 BALTIMORE 10 MD 4ESS (08/1980) 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) 016 CHARLESTON 2 WV 4ESS (02/1982) 017 CLEVELAND 3 OH 4ESS (12/1979) 018 COLUMBIA 2 SC 4ESS (11/1981) 019 COLUMBUS 3 OH 4ESS (04/1977) 020 COLORADO SPRINGS 2 CO 4ESS (10/1981) 021 CAMBRIDGE 19 MA 4ESS (12/1984) 022 CAMDEN 3 NJ 4ESS (04/1979) 023 CINCINNATI 2 OH 4ESS (06/1979) 024 DES MOINES 2 IA N4E Replaced 025 DALLAS 3 TX 4ESS (12/1976) 026 DALLAS 4 TX 4ESS (04/1981) Possibly replaced with 154-T? 027 DENVER 5 CO 4ESS (11/1979) 028 DETROIT 3 MI 4ESS (04/1981) (Disconnected circa 2003?) 029 DAYTON 2 OH 4ESS (02/1987) 030 FREEHOLD 2 NJ 4ESS (05/1978) 031 FRAMINGHAM 4 MA 4ESS (05/1987) 032 FORT WORTH 2 TX N4E Replaced 033 GRAND RAPIDS 3 MI 4ESS (05/1984) 034 GREENSBORO 3 NC 4ESS (03/1981) 035 GARDENA 3 CA 4ESS (06/1987) 036 HARRISBURG 2 PA N/A Replaced Changed to a 5ESS 037 HOUSTON 4 TX N4E Replaced 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) Caribbean gateway 042 KNOXVILLE 2 TN 4ESS (12/1980) 043 KANSAS CITY 2 MO N4E Replaced 044 LANSING 3 MI 4ESS (05/1987) 045 LOS ANGELES 5 CA 4ESS (02/1983) 046 LOS ANGELES 6 CA 4ESS (04/1988) 047 LOUISVILLE 2 KY 4ESS (07/1980) 048 LITTLE ROCK 2 AR N4E Replaced 049 MACON 3 GA 4ESS (04/1987) 050 MIDLAND 2 TX 4ESS (10/1983) 051 MEMPHIS 2 TN 4ESS (02/1981) 052 MANCHESTER 3 NH 4ESS (04/1982) 053 (presently unassigned) N/A N/A N/A 054 MINNEAPOLIS 3 MN 4ESS (05/1980) Canadian Gateway 055 MINNEAPOLIS 4 MN 4ESS (06/1988) 056 MONTGOMERY 2 AL N4E Replaced 057 NORFOLK 4 VA 4ESS (04/1981) 058 NASHVILLE 2 TN N4E Replaced 059 NEW HAVEN 5 CT 4ESS (10/1981) 060 NEW ORLEANS 3 LA 4ESS (06/1980) 061 NEWARK 8 NJ 4ESS (06/1980) 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 "(Regal Park, QUEENS)" 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 072 ORLANDO 3 FL 4ESS (09/1980) 073 PEORIA 3 IL 4ESS (02/1983) 074 PHILADELPHIA 4 PA 4ESS (05/1980) 075 PHOENIX 3 AZ 4ESS (09/1980) 076 PITTSBURGH 3 PA 4ESS (11/1977) 077 PORTLAND 3 OR 4ESS (04/1979) Alaska Gateway 078 RICHMOND 2 VA 4ESS (05/1979) 079 ROCKY MOUNT 3 NC 4ESS (06/1982) (was United-Carolina) 080 ROCHELLE PARK 3 NJ 4ESS (08/1982) 081 RENO 4 NV 4ESS (05/1982) 082 SOUTH BEND 3 IN 4ESS (04/1987) 083 SACRAMENTO 4 CA N4E Replaced Hawaii gateway 084 SHERMAN OAKS 5 CA 4ESS (06/1985) Pacific gateway 085 STOCKTON 3 CA 4ESS (03/1984) 086 SALT LAKE CITY 2 UT 4ESS (04/1982) Canadian Gateway 087 SAN ANTONIO 2 TX 4ESS (05/1977) Mexican gateway 088 SAN DIEGO 3 CA N4E Replaced Only heard locally 089 SAN FRANCISCO 4 CA 4ESS (06/1985) 090 SAN JOSE 3 CA 4ESS (03/1982) 091 SPRINGFIELD 2 IL 4ESS (04/1985) 092 SPRINGFIELD 3 MA 4ESS (05/1980) Canadian Gateway 093 SPOKANE 2 WA 4ESS (10/1982) Canadian Gateway 094 SAINT LOUIS 3 MO N4E Replaced 095 SEATTLE 4 WA 4ESS (05/1980) Canadian/Alaska Gateway 096 SYRACUSE 2 NY 4ESS (03/1985) 097 TAMPA FL 4ESS (11/1986) 098 TOLEDO 2 OH 4ESS (04/1984) 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) Atlantic gateway 104 WHITE PLAINS 5 NY 4ESS (08/1980) Canadian Gateway 105 WAUKESHA 3 WI 4ESS (03/1979) 106 WEST PALM BEACH 4 FL 4ESS (08/1981) Caribbean gateway 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 4ESS (11/1988) Atlantic gateway 112 PLYMOUTH 2 MI 4ESS (12/1989) 113 SAN BERNARDINO 2 CA 4ESS (03/1989) 114 TUCSON 3 AZ 4ESS (10/1989) 115 PITTSBURGH 9 PA 4ESS (12/1988) Atlantic gateway 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) 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) 124 PLANO IL 4ESS (12/1992) (standby tandem) 125 ELLISVILLE FL 4ESS (10/1992) 126 MONTICELLO 2 GA 4ESS (10/1992) 127 CEDAR KNOLLS 2 NJ 4ESS (10/1992) 128 TACOMA 2 WA 4ESS (12/1992) 129 DUNNIGAN CA 4ESS (06/1993) 130 GARDENA 4 CA 4ESS (04/1993) Possibly replaced with 152-T? 131 FORT LAUDERDALE FL 4ESS (05/1993) 132 MADISON 3 WI 4ESS (11/1992) 133 WHITE PLAINS 4 NY 4ESS (08/1993) 134 MARKHAM ON (905-U2) 4ESS (06/1993) UNITEL (Canada) 135 CHERRYVILLE NJ 4ESS (05/1993) 136 CAMBRIDGE MA 4ESS (06/1993) 137 ALDERGROVE BC (604-U2) 4ESS (08/1993) UNITEL (Canada) 138 OXNARD CA 4ESS (07/1993) 139 ANCHORAGE AK 4ESS (03/1996) ALASCOM 140 MESA AZ 4ESS 2nd Gen (1998/1999) 141 DURHAM NC 4ESS 2nd Gen (1998/1999) 142 DENVER 6 CO 4ESS 2nd Gen (1998/1999) 143 FORT MYERS FL 4ESS 2nd Gen (1998/1999) 144 MONROVIA MD 4ESS 2nd Gen (1998/1999) 145 CHICAGO IL 4ESS 2nd Gen (1998/1999) 146 ATLANTA GA 4ESS 2nd Gen (07/1999) Last #4ESS 147 CHICAGO IL (?) N4E 2012? 148 BOSTON MA (?) N4E ? 149 ??? AZ (?) N4E ? Possibly replaced 140-T? 150 ATLANTA GA (?) N4E ? 151 ??? FL (?) N4E ? Fort Myers/Naples area 152 GARDENA CA (?) N4E (08/2013) Possibly replaced 130-T? 153 ??? MA (?) N4E ? 154 DALLAS TX (?) N4E ? Possibly replaced 026-T? 155 ??? AZ (?) N4E ? Phoenix metro (Scottsdale?) 156 SYRACUSE NY (?) N4E ? Possibly in addition to 096-T? 157 JACKSONVILLE FL (?) N4E ? Possibly replaced 041-T? 158 ANAHEIM CA (?) N4E ? Possibly replaced 004-T? 159 ??? PA (?) N4E 2016? Possibly replaced 101-T?