Echo Oscillation is a Continuous Trap Card.
Trap Cards are normally Set first and can be activated on a later turn, often in response to an action.
On the current TCG and OCG Forbidden & Limited lists tracked here, Echo Oscillation is Unlimited.
YGOPRODeck lists Echo Oscillation for these formats: Common Charity, TCG, OCG, Master Duel.
A listed print of Echo Oscillation appears in 2015 Mega-Tin Mega Pack (MP15-EN243) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Echo Oscillation is about $0.01 on TCGPlayer (prices change frequently).
