"When the ram's horn sounds": (lit.,) when the ram's horn "draws out" its sound, you may ascend the mountain. R. Yossi says: It is not a man's place that honors him, but he that honors his place. As long as the Shechinah was on the mountain — "Whoever touches the mountain shall be put to death." Once the Shechinah has left the mountain, all are permitted to ascend it.
When the Ram's Horn Sounds Lit
Mekhilta Tractate Bachodesh 3:14