As of 2023-11-22 you can dial 800-488-0097 to discover which switch MCI routes calls through. Listen to the entire intercept to get a feel for the behavior of the switch. Behavior is different when comparing DEX tandems to DMS tandems. The list below is based from https://telephoneworld.org/long-distance-companies/mci-tandem-list/ and enhanced/maintaned by ThoughtPhreaker with many years of network exploration. We thank you for your service. Many of these switches are still in service. ID SWITCH REGION LOCATION NOTES 211 PRY2 MID ATL DEX, serves Baltimore, MD 212 CHT1 NOR EAST DMS, via calling card platform, no timeout via SS7? 213 WPL2 NOR EAST White Plains NY 215 BRW2 MID WEST DEX Serves 419 area of Ohio, 810 area of Michigan 216 WRG4 MID ATL DEX Serves Freehold, NJ area 21A AUB2 SO EAST Auburn AL? KY? DEX Serves Tampa, FL area 21B DNJ1 WEST Denver CO DEX 21C SAJ3 SO WEST San Antonio TX DEX 21E BRK1 SO WEST Brownsville TX? DMS 21F GRN2 SO EAST Greensboro NC DEX 21G CHT2 NOR EAST Charlton MA? DEX 21H RIA1 PACIFIC Rialto CA DEX 21K CRJ1 SO WEST Corpus Christi TX DEX Possibly elsewhere? Heard in Illinois, Missouri 21L DNJ2 WEST Denver CO DMS 21M SEJ5 WEST Seattle WA DMS,Canada Gateway? 21N LUB2 SO WEST Lubbock TX? DMS 21Y POT2 MID ATL DEX Weirdly edited (digit by digit) sounding ID, serves 570 region of PA 23E SCR2 PACIFIC Sacramento CA DMS 23I MEM2 SO EAST Memphis TN DEX 23J WYV2 MID WEST DEX Serves Cincinatti or surrounding area? 23K IRV3 SO WEST Irving TX? DEX 23N POT1 MID ATL DMS,Canada Gateway? 23T HLB2 NOR EAST Hillsborough, NJ? DEX, used for international gateway - inbound UK 25I OMJ2 WEST Omaha NE DEX 2AK DMG1 PACIFIC DMS, Hawaii gateway 2AL SFC3 PACIFIC San Francisco CA DMS, Hawaii gateway, 2CB uses this switch for payphone block recording 2AM SHO1 PACIFIC Sherman Oaks CA DEX 2AP JKV1 SO EAST Jacksonville FL DEX 2AZ HOU6 SO WEST Houston TX DMS, shitty trunks to LA 4/16/13 2BE DNG2 MID WEST DMS 2BF IPL2 MID WEST Indiannapolis IN DEX 2BG PIT4 MID ATL Pittsburgh PA DMS 2BJ IRV2 SO WEST Irving TX? DMS, via calling card platform, no timeout via SS7? 2BK NYCD NOR EAST New York City NY 2BL NEO1 SO EAST New Orleans LA 2BM WRG2 MID ATL DMS, Worldcom sends UIFNs via here 2BP AST2 SO EAST Austell GA DMS 2BR GRN1 SO EAST Greensboro NC DEX 2BZ NYCE NOR EAST New York City NY DMS 2CB HAY1 PACIFIC Hayward CA DMS, Used in Florida. Actually there? 2CD BRW1 MID WEST Bridgewater, MI? DMS 2CE DMG2 PACIFIC DMS, trunks w/discomfort noise to NYC? Tried again 2/5/13,4/13/13, no discomfort noise 2CG WAS6 MID ATL Washington DC DMS 2CH PHL6 MID ATL Philadelphia PA DMS 2CJ WIT1 WEST (several possible AZ) DMS 2CK NRL1 MID WEST Ohio? DEX Canada Gateway 2CL DAL9 SO WEST Dallas TX DEX 2CQ PRY1 MID ATL DMS 2CS WSP1 MID WEST Illinois? DEX 2CT WYV1 MID WEST Waynesville, OH DMS 2BF uses this for verification rec; possibly WV? KY? 2CU WPL1 NOR EAST White Plains NY DMS, inbound UK gateway 2CV AUB1 SO EAST Auburn AL? KY? 2CX NBW1 MID ATL New Brunswick NJ? DMS 2CY SRD1 NOR EAST Springfield MA? DEX Canada Gateway 2CZ IDC2 SO WEST Independence MO? DMS? ACY uses this for verification rec 2D4 POB1 SO EAST DEX, announcement ID said unusually quick 2DK MIM3 SO EAST Miami FL DMS, inbound UK gateway 2EA RIC2 MID ATL Richmond VA DMS, 5156 Francistown Road, Glen Allen, VA 2EB NRL2 MID WEST DMS, Canada Gateway?, UK gateway, got via Ohio 2ED MNJ1 WEST Minneapolis MN DMS 2EE HOU5 SO WEST Houston TX DEX 2EF PHI7 MID ATL Phildelphia PA DMS 2EG OMJ1 WEST Omaha NE DMS 2EH HAY2 PACIFIC Hayward CA DEX, Pacific gateway? 2EJ AST3 SO EAST Austell GA DEX 2EK SEJ1 WEST Seattle WA Canada Gateway, DEX 2EL WSP2 MID WEST Wisconsin? DEX 2E0 RIA2 PACIFIC Rialto CA DMS 2HH IRV1 SO WEST Irving TX? DMS 2II DNG1 MID WEST Possibly Texas? DMS 2OP HLB3 NOR EAST (Southern NY) DMS, shitty trunks via calling card platform 2QQ ATL2 SO EAST Atlanta GA DEX 2RR AST1 SO EAST Austell GA DMS 2XX WAS5 MID ATL Washington DC DMS, inbound UK gateway 2ZZ IDC1 SO WEST Independence MO? DMS A07 DNJH WEST Denver CO A26 WAS7 MID ATL Washington DC DMS, ID done with TTS AAD WIT6 WEST (several possible AZ) DEX, Tucson area? ACY MNJK WEST Minneapolis MN DEX AGQ CHTG NOR EAST DMS (Verify this isn't in Arizona) AGW RCH1 SO WEST Richardson TX? DEX AHA HAYD PACIFIC Hayward CA DMS AHC ? ? ? DMS, shitty trunks via calling card platform AUL SAR1 PACIFIC Utah DMS AWT ATLC SO EAST Atlanta GA DMS AYB ??? NOR EAST White Plains NY? DMS, inbound UK gateway AYM PLV3 MID ATL DEX, ID partly cut off AYU RIA6 NOR EAST ELB ELM1 NOR EAST VNet uses 21M, 2BZ, 2OP, 2HH, 2CS