---
title: "Eligible Mode S interrogator — EASA Definition · Avioverse"
description: "Article 2, Regulation (EU) 2017/373: ‘eligible Mode S interrogator’ means a Mode S interrogator for which at least one of the following conditions is…"
url: "https://avioverse.aero/glossary/easa/eligible-mode-s-interrogator"
---

# eligible Mode S interrogator

EASA defines “eligible Mode S interrogator” in one regulation. The wording below is reproduced verbatim from the EASA Easy Access Rules, with a link to the paragraph it comes from.

> ‘eligible Mode S interrogator’ means a Mode S interrogator for which at least one of the following conditions is satisfied:
>
> (a) the interrogator relies, at least partly, on Mode S all call interrogations and replies for Mode S targets acquisition;
>
> (b) the interrogator locks out acquired Mode S targets in reply to Mode S all call interrogations, permanently or intermittently, in part or the totality of its coverage; or
>
> (c) the interrogator uses multisite communications protocols for data link applications;

Article 2 · Air Traffic Management / Air Navigation Services · Regulation (EU) 2017/373 · Easy Access Rules, 12 Mar 2025 revision · [Read Article 2](https://avioverse.aero/regulations/easa/atm-ans/cover-regulation/powers-and-recitals#article-2)

## Defined in the same article

- [airborne collision avoidance system (ACAS)](https://avioverse.aero/glossary/easa/airborne-collision-avoidance-system)
- [ATM/ANS provider](https://avioverse.aero/glossary/easa/atmans-provider)
- [data services provider (DAT provider)](https://avioverse.aero/glossary/easa/data-services-provider)
- [design of airspace structures](https://avioverse.aero/glossary/easa/design-of-airspace-structures)
- [harmful interference](https://avioverse.aero/glossary/easa/harmful-interference)
- [interrogator code allocation plan](https://avioverse.aero/glossary/easa/interrogator-code-allocation-plan)
- [Mode S interrogator](https://avioverse.aero/glossary/easa/mode-s-interrogator)
- [Mode S operator](https://avioverse.aero/glossary/easa/mode-s-operator)