| Telco | Circuit Format |
|---|
| Aliant Communications | FDDS |
| AT&T | DHEMxxxxxx, DZEKxxxxxx |
| Ameritech | HFGS, DHZA, IBZD |
| Bell Atlantic | xx-HFGQ-xxxxx, xx-HCGL-xxxxxx, HCGA, xx-YGGA-xxxxxx, xx-ASTZ-xxxxxx, xx-YBGA-xxxxxx, xx-YBGS-xxxxxx, xx-YGGA-xxxxxx |
| Brooks Fiber | 27.xxxx xx/HCXA/xxxxxx |
| ELI | HCFL/xxxxxx/xxx, DHFL/xxxxxx/ELG |
| Frontier | LTC-xxxxxx |
| GTE | 85/YBGS/xxxxxx, 85/HCGS/xxxxxx, 2/QJDA/xxxxx, 2/UHMA/xxxxx, x.QGDQ.xxxxxx, x.QGGQ.xxxxxx |
| Hyperion | HFGA |
| MCI | MGX-xxxxxxxxx, MHY-xxxxxxxxx |
| MFS | 13X-xxx-xxx-xxxx,13-xxx-xxx-xxxx, 3x-xxx-xxx-xxxx, 1x-xxx-xxx-xxxx |
| Nynex | xx-DHZN-xxxxxx |
| NCA | CNA |
| Pacific Bell | xxYBRQxxxxxx, xxYBQQxxxxxx |
| PacWest | xxhcfsxxxxxx-xxx |
| QWest | SPA |
| Sprint | 3x-xxx-xxx-xxxx |
| Southwestern Bell | 97.xxxx 98.xxxx xxHXGKxxxxxx, xxHCGSxxxxxx, xxDHDAxxxxxx, xxIBJDxxxxxx |
| Sprintlink | PL1 |
| TCG | xx-ASxx-xxxxxx |
| WorldComm | WZ.xxxx |
| US West | 51.xxxx.xxxx 4x.xxxx.xxxx, xxYBGAxxxxxx, xxHCGLxxxxxx, xxHCGSxxxxxx |