The following types of serial identification data can be encoded in beacons using the serial user protocol:
- identification serial number;
- 24-bit aircraft address number;
- aircraft operator designator and a serial number.
Bits 40 – 42 indicate the beacon type with serial identification data encoded as follows:
| 000 | indicates an aviation ELT serial number is encoded in bits 44-63; |
| 010 | indicates a maritime float free EPIRB serial number is encoded in bits 44-63; |
| 100 | indicates a maritime non float free EPIRB serial number is encoded in bits 44-63; |
| 110 | indicates a personal locator beacon (PLB) serial number is encoded in bits 44-63; |
| 011 | indicates the aircraft 24-bit address is encoded in bits 44-67 and each additional ELT on the same aircraft is numbered in bits 68-73; |
| 001 | indicates an aircraft operator designator and a serial number are encoded in bits 44-61 and 62-73, respectively. |