| AVL | Automatic Vehicle Location — record containing time, GPS fix, IO elements, etc. |
| IMEI | International Mobile Equipment Identity; primary key for tracker hardware in this project (devices.imei). |
| Codec 8 | Teltonika binary codec for AVL data over TCP (payload ID 0x08). |
| Codec 8 Extended | Variant (0x8E) with larger IO space. |
| Codec 12 | Teltonika codec for GPRS commands (configuration, getinfo, etc.) — request/response on the same TCP session. |
| Acknowledgment (AVL) | After a valid Codec 8 packet, the server sends 4 bytes big-endian integer: number of records accepted. Wrong ack → device may retry or stop. |
| Idempotency | Command queue uses idempotency_key per IMEI so retries do not duplicate logical commands. |
| Gateway | services/telematics-gateway — process that speaks Teltonika TCP, not HTTP. |
| OmniTrack API | server.ts — HTTP JSON APIs used by the web UI and integrations. |