Kommunikations- og navigationsudstyr, der allerede er godkendt, behøver ikke at overholde en revideret ETSO eller en revideret specifikation ud over ETSO, medmindre der foreskrives et krav med tilbagevirkende kraft.
Communication and navigation equipment which has already been approved does not need to comply with a revised ETSO or a revised specification, other than ETSO, unless a retroactive requirement is prescribed.