Nynex Telephone Network Troubleshooting
PDI 122 0 156 187 Central office
PDO 135 153 0 200 Customer’s wiring
PDF 160 178 194 0 Cable facility
Mistaking a PDI for a PDT has a cost of 122
These aren’t actual NYNEX costs, so don’t try think you can start a company to troubleshoot telephones