As long as it doesn't specifically say when you play it, you can play an Equipment card at any time, whether it is your turn or someone else's turn. Just loundly declare to the table 'STOP' and then play your card face-up on the table.
You MAY play it in response to someone taking a specific ACTION, but before that action is resolved. The player who declared the action may choose a different action to take after the Equipment is resolved if the Equipment prevented them from taking an action.
You may NOT play an Equipment card in response to another Equipment card being played. The first Equipment card must be fully resolved before other Equipment cards may be played.
When we talk about PLAYING an Equipment card, that means taking it out of your hand, putting it face-up on the table. If an Equipment card is already on the table, when its effect is triggered, you're not PLAYING it, so its effect could prevent the effect of another Equipment card.
