What is the specific legal effect when a speed limit sign (e.g., '30 km/h') is placed directly on the same post as a town entrance sign (panneau d'entrée d'agglomération)?

1. The 30 km/h speed limit applies throughout the ENTIRE built-up area on all streets, unless otherwise signposted
2. The 30 km/h speed limit applies only on the specific entrance avenue for the first 100 meters
3. The speed limit applies only to commercial trucks and buses entering the town
4. The town entrance sign cancels the speed limit sign