SCH2500 - 2599
| SCH2501 | An attempt was made to change a telephone that is in the process of relocating. |
| SCH2502 | A request other than NEW or OUT was used in conjunction with type CARD. |
| SCH2503 | An attempt was made to service change a telephone that SET-RELOCATE was working on. |
| SCH2504 | An invalid TN was entered when adding or removing a card. |
| SCH2505 | An attempt was made to remove a card that has equipped units. |
| SCH2506 | An attempt was made to change a set that belongs to a different customer. |
| SCH2507 | An attempt was made to change a set that is busy. |
| SCH2508 | ALOW or DENY was expected as an input but was not received. |
| SCH2509 | An invalid Prime DN has been entered. It is not unique or is not a Prime DN. |
| SCH2510 | Attendant Administration Package is not equipped. |
| SCH2511 | History File feature package restricted. |
| SCH2512 | Not enough PDS to allocate History File of requested size. Followed by (allocated size) and (requested size). |
| SCH2513 | Invalid user for History File. |
| SCH2514 | History, traffic or TTY file is empty. |
| SCH2515 | No new messages added to History File since last printout. |
| SCH2517 | Attendant Overflow Position package restricted. |
| SCH2521 | Not enough digits entered. |
| SCH2522 | Invalid entry for prompt CFW (not DENY or CFW). |
| SCH2523 | Invalid entry for prompt SPC (not DENY, SCC, or SCU). |
| SCH2524 | An attempt was made to assign an ACD or MC key to an SL-1 set. |
| SCH2525 | Mini-CDR package is not equipped. |